Well, about the validity of the book (for the Quran at least) I can only say that reading it would be your best option and then later one can decide if it is true or not. For example, if someone says that the Harry Potter books are rubbish or Twilight is the best written thing, I can only give my opinion by reading said books, no? I can explain and explain all that I want, but the only thing that works with or against me is your opinion after reading the book.
Within the context of worship, the most important role is played by the imam, who serves as the prayer leader. Most mosques, especially large ones, have a permanent imam who functions in this capacity on a full-time basis. In smaller mosques it is more common to rotate leaders from among the community so that no one person is identified with the role. The backgrounds and qualifications of imams vary considerably, and they function independently of each other If you want more information on this, here is a website I often rely on: Christanity has a Bishop, what does Islam have? However, just like many other religions, Islam has its sects as well: Sunni and Shia, and it both the job of the Imam varies. Here is a link that explains the differences, if you're interested: Sunni and Shias
Now for your final question as to why I believe in a God, I hope this analogy works: consider the universe, and everything contained within it, as a marvellous and beautiful diorama. Everything has been planned out, and is exactly where it is supposed to be. The planets have been put in such a place that if it were even moved ten inches, there would be planetary collisions; the earth’s position relative to the sun is perfectly placed to sustain life, not too far (like Pluto), or not too close (like Mercury); the raindrop has been put in perfect position to sun rays to create a rainbow, etc. Now what often people argue is that clay, glue, paint, and other such materials were used to create the diorama. But what they often forget is that there must be a Master artist whose hands are responsible for all of this.
I don’t mind – I’m just happy to spread the knowledge! And even if you still don’t believe, I don’t mind for God says,
“There shall be no compulsion in [acceptance of] the religion.” [2:256]
Some facts regarding the prophethood of Muhammad (saw).
1. The Prophet (saw) was illiterate.
2. The Prophet (saw) grew up in a pagan society. He was extremely upset over their practices and began meditating over the universe. This became very apparent when the Prophet (saw) became 35 years of age and spent every Ramadan in a cave on the outskirts of Mecca known as the Cave of Hira.
3. In 610 AD, the Holy Prophet (saw) received his first revelation – the verses of Surah Alaq. After the whole event, he was badly shaken and wished to commit suicide. He was comforted by his wife, Hazrat Khadija (ra). He was taken to her cousin (who was Christian). Upon hearing the event from the Prophet (saw), he confirmed his as the final messenger of Allah, which was foretold in the Bible.
If the Holy Prophet (saw) was disheartened by such practices, why did he wait to write a book? Why would he wait for 40 years before preaching against paganism? And why would he want to commit suicide if he wrote the book? And how could an illiterate man write a book?
4. When the Holy Prophet (saw) got over his shock, he began preaching Islam – which faced much fierce opposition from the pagans of Mecca. And people who began to accept Islam were brutally tortured, but the Prophet (saw) received double the torture any of the followers had to endure. People made fun of him, threw sticks and stones at him, and even went as far as to assassinate him.
If Islam was manmade, why would the Holy Prophet (saw) endure so much torture? And the pagans of Mecca even bribed him, which he refused. And it was no simple bribe, had he accepted it and denounced Islam, he would’ve been the richest man of his time as well as the most famous! No one would decline such a bargain, if the religion he was preaching was made up.
Here are some links you might consider reading:
Another thing that might cause shadow of doubts regarding the validity of Islam and the Quran is that it might’ve be tampered with like the Torah and Bible were. However, I assure you that the Quran has not been played around with and is the same book it was 1400 years ago. How the Quran was preserved for generations to come is explained best in the links, as it is quite long:
The reason I compared the scenario with Harry Potter and Twilight is that no matter how much I argue and explain, the only way you’re question may truly be answered is by reading the book in itself. And the same goes for factual books. How am I to tell if the book is true or not without reading it? If one has not read the source material, how can one be a judge of it? As a wise teacher once told me, "You can't give an exam based on opinion."