You don't need to be able to read and understand Ancient Arabic.
It is 'cleaner' to stick to authorised translations, yes they exist otherwise non-Arabic reading Muslims would have no texts to follow.
At the very least you will need to following texts in your bookshelf and you will need to have at least read them and have a basic familiarity with them:
The Koran - e.g. Abdullah Yusuf Ali
The Life of Muhammed - e.g. Guillaume
The Haddith - e.g. Sahih Al Bakhari - Available online as well.
Reliance of the Traveller - e.g. ibn Naqib Al Misri a.k.a. the Sharia Law Book.
If you don't have these, haven't read them or don't know what they are then not only should you not comment on Islam, you probably know very little or nothing about the religion.
The next best source of information is from former Muslims who have lived the life, been raised in the societies and been trained in the texts. These include:
Ayaan Hirsi Ali, Ibn Warraq, Bat Ye'or
Next are those who have studied the texts, researched the practices, the history, the lives and kept track of modern events. These include:
Robert Spencer, Bruce Bawer, Melanie Phillips, Raymond Ibrahim, Daniel Pipes and many others
You should also read the apologists to see how the truth it manipulated. The original source in modern times is Edwards Said's "Orientalism" but others like Karen Armstrong are also essential reading.
Finally there are various Blogs and Web sites that cover the subject in some depth. These include:
Jihad Watch, Atlas Shrugs, Islam Review and so on.
An excellent starting point is www.jihadwatch.org.
You will need to read a lot, compare a variety of different viewpoints and gradually the whole tapestry will become clear.
