You're in high school. I think it's fairly appropriate. Hell, I was playing Doom when I was 9 years old. If you're even 14 years or older, it's perfectly fine to play the game.

only mature game I played was Eternal Darkness... didn't change my life in any way

Theres really nothing to bother you exept the violence. Theres no sex, the blood isnt going to scare anyone, so i dont see any realy reason why you should play the best game of the 21st century.

I'm finding it really hard to take this seriously when you have a No More Heroes avatar.

To answer your last question, no the game isn't very hard. It's probably the easiest Resident Evil ever because of an abundance of ammo throughout the game.

Yes play it, bring down the system, ratings are BS and you should have fun with one of the best games ever made. (hype up my editorial a bit before I finish it lol)

I played M rated games when i was 10, and i turned out ok.

Conclusion: If you are not a psycho who tries to attempt dangerous in game events in real life, for example going around and shooting people, you will be fine.

I think you'll be fine. As long as you don't go around chainsawing people afterwards you should be alright. But if ya really don't know ask your parents or let them play it and see if they'll let ya.

Its a little more forgiving than the earlier Resident Evil games- more weapons and ammo to kill the bad guys with. It can be freaky at points. If you start getting spooked, stop playing and go watch some TV for a while. Come back to it later on when your nerves are settled. Its kinda gory, so if that goes against any religious beliefs, you might find it offensive. If so, stop playing it.