Echoing other sentiments: slow it down. Maybe even pick another song. You want to play Slayer, take a shot at South of Heaven. It's slower and little easier to get a handle on for someone who hasn't built up the speed and accuracy yet. I'd suggest maybe digging into the Sabbath catalog. There are some great songs there that you can pick up pretty quick and play with better accuracy.

I say this from experience. Part of the reason that I'm a lousy guitar player after 20 years of playing is that I didn't have patience. I didn't like playing a song over and over and over and over in slow motion (still don't, to be honest), and I figured that playing the song I wanted to play half-assed was better than the alternatives. Now I really want to go back and learn like I should have, but I've got a ton of bad habits that are going to make it a struggle.

I hope you take the advice here and use it. I would have loved to have had Internet and a forum like this when I started. I give you tons of credit for having guts. I've got about 20 years experience on you, and I'm not about to post my version of Raining Blood. :D