Well to start, although
the quran teaches its followers to kill unbelievers such as Christians (Sura 2.191), there is no need to approach the study of islam with fear because islamophobia (fear of islam) is frowned on. At first, I could not help but feel a little fear towards the religion but as a Christian, my faith no longer permits fear. I can now calmly debate muslims who care to listen and avoid the fanatics who would not care to listen anyways.
This site is extremely useful for study. It has an index that is very helpful for beginners:
[Good Site]
As to your question on "sinful nature"; I just explained to someone the difference between veil-use amongst Christian females compared with niqab-use amongst muslim females.
Veils amongst Christians are used out of the woman's respect for God. For since men were created first and angels seem to feel disturbed by women praying without veil, women wear a veils.
Niqabs are full head to toe coverings amongst muslim females. They wear these to keep men from feeling tempted. Should so much as an ankle show from below the niqab, a man could be provoked and the woman could then legally be reprimanded (in some cases flogged). Looking at rape, a woman raped has no legal recourse for justice because sharia court would view her as the culprit for displaying skin and provoking the assailant. The assailant would be considered innocent.
As you can see, "sin" is not defined as Christians recognize sin. In many cases, what is considered wrong is right with them, and what is right is wrong with them.