Giving the adhaan, coming early to prayer and taking care of the mosque are all great acts of worship and beneficial righteous deeds which are encouraged in Islam, in many well-known ahaadeeth. 

The texts also speak of the virtue and honourable status of knowledge and encourage us to seek it. 

It should be noted that seeking knowledge may be an individual obligation (fard ‘ayn), i.e., the knowledge that makes one’s belief (‘aqeedah), worship and actions correct. It is not permissible to neglect this kind of knowledge or to be distracted from seeking it, either by the adhaan or anything else. 

The knowledge that is essential includes: knowledge of ‘aqeedah (belief, doctrine) and Tawheed in general, knowledge of the rulings on prayer and fasting, knowledge of the rulings on zakaah for those who have wealth on which zakaah is due, and knowledge of the rulings on Hajj for those who want to go to Hajj. 

It is also essential to know the rulings on buying and selling for those who want to engage in that; rulings on marriage and divorce, food and drink, and other actions and transactions in which people may wish to engage. 

Al-Mannaawi (may Allaah have mercy on him) said: There are nearly twenty different opinions regarding what areas of knowledge should take precedence, all of which offer evidence to support their view. The best that can be said is what al-Qaadi said: What we cannot do without knowing, such as knowledge of the Creator (Allaah, may He be exalted and glorified) and the Prophethood of His Messengers, and how to pray etc., knowing these things is an individual obligation. 

Fayd al-Qadeer, 4/267. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: Seeking Islamic knowledge is a communal obligation (fard kifaayah); if sufficient people undertake it, then for the rest it becomes Sunnah. And seeking knowledge may be an individual obligation. The guideline is if it is needed for an act of worship that he wants to do or a transaction or interaction he wants to engage in; in that case he must learn how to worship Allaah by doing this act of worship, and how to undertake that transaction etc. Apart from that, seeking knowledge is a communal obligation and the seeker of knowledge should feel that he is undertaking a communal obligation so that he will attain the reward for undertaking an obligation as well as gaining knowledge. 

From Kitaab al-‘Ilm. 

You have done well by bringing the CDs of the lessons, because that is a means of seeking knowledge, although it does not mean that you do not need to sit with the scholars and learn from them, and ask them about anything you do not understand. 

It seems that in your situation, where you are trying to decide whether it is better to give the adhaan and take care of the mosque, or to seek knowledge that is not an individual obligation, that you should try to combine the best of both, by regularly attending some classes, and continuing to look after the mosque, and make up for the classes you miss by using the CDs, as well as asking the scholars about anything you do not understand. If the administration of the mosque do not agree with you being absent sometimes, then give precedence to seeking knowledge, for it is a source of honour and status in this world and in the Hereafter, especially since there will never be a shortage of people to give the adhaan and take care of the mosque, but those who are serious in the pursuit of knowledge are few and far between. 

Ibn al-Qayyim (may Allaah have mercy on him) said, explaining the virtue of knowledge:  (108): Many of the imams clearly stated that the best of deeds after the obligatory duties is seeking knowledge. Al-Shaafa’i said: There is nothing after the obligatory duties that is better than seeking knowledge. This is what his companions narrated was his opinion. This was also stated by Sufyaan al-Thawri, and the Hanafis narrated this from Abu Haneefah. Three opinions were narrated from Imam Ahmed: 

The first was that the best of deeds after the obligatory duties is seeking knowledge, because it was said to him: “What thing is dearest to you, for me to sit at night copying (texts) or to offer voluntary prayers? He said: Your copying (texts) and learning about your religion from it, that is dearer to me. Al-Khallaal quoted many texts from him in Kitaab al-‘Ilm about the virtue of knowledge, for example, he said: People’s need for knowledge is greater than their need for food and drink. 

The second is that the best of deeds after the obligatory duties is voluntary prayer, and he quoted as evidence for this the words “Know that the best of your deeds is prayer” and the hadeeth of Abu Dharr, when he asked him (the Prophet (peace and blessings of Allaah be upon him)) about prayer and he said “(It) is the best that has been prescribed.” And he quoted the fact that the Prophet (peace and blessings of Allaah be upon him) advised the one who asked to be close to him in Paradise to do a lot of prostration, i.e., prayer, and the fact that in another hadeeth he said: “You should prostrate, for you do not do one prostration for Allaah, but Allaah will raise you one degree (in status) thereby and will remove one sin from you thereby.” And there are many other ahaadeeth which speak of the virtue of prayer. 

The third opinion is that jihad is the best of deeds, and he (Imam Ahmad) said: I cannot think of anything that matches jihad. And there is no doubt that most of the ahaadeeth speak of prayer and jihad. 

With regard to Maalik, Ibn al-Qaasim said: I heard Maalik say: Some people pursued worship and ignored knowledge, then they engaged in an armed rebellion against the ummah of Muhammad. If they had sought knowledge, it would have prevented them from doing that. Maalik said: Abu Moosa al-Ash’ari wrote to ‘Umar ibn al-Khattaab (saying) that there are people with us who read the Qur’aan, such and such a number of them. ‘Umar wrote back to him, telling him to allocate them a stipend from the bayt al-Maal (treasury of the Islamic state). The following year, he wrote to him saying that many people, more than before, were reading the Qur’aan. ‘Umar wrote back to him telling him to erase their names from the record saying, “I am afraid that people will be hasty in reading the Qur’aan and will not understand the religion properly, then they will distort its meanings.” Ibn Wahb said: Maalik ibn Anas was in front of me and I put my tablets down and got up to pray, and he said: “What you have got up for is better than that which you have left.” From Miftaah Daar al-Sa’aadah, 1/119. 

And Allaah knows best.