Dude,
totally go for it! You sound like you have a well defined goal, and are very comfortable and confident with your level of risk taking. We all gotta start somewhere, regardless if it is an ideal situation for acheiving the 'best' sound. You may run into some fustration but big deal...if you got the right personality for it then its a challenge and not a dead end.
Something to consider: Instead of renting a mixer/power amp etc. for use with your computer, see if they have an "all-in-one" multracker for rent. Some of them (VF16/Yammaha) have the potential to simplify your set up, will provided enough preamps/inputs, have easy "tape-like" operation, and might reduce the learning curve to the most essential things (like picking and setting your mics). You will also avoid any PC problems that have been previously mentioned. You would also have the advantage of having each drum mic on a seperate track - a very good idea if your new to mixing/recording drums. However, i got bandmates who are not very computer savy at all, who learned cubase and were multrack recording (on a non-audio dedicated computer) within 3 days!
I wouldn't get that picky about the mics at this point - go to the microphone forums "FAQ" section - there is an excellent guide on their for choosing everything you want to record, from drums to guitars to vocals. Print the appropriate sections out and take it with you to the store. Since your really new at capturing the sounds, then it would probably help if the sounds themselves are the best they can be - RENT THE REAL AMPS!!!!! That's a subjective call, but uhmm...RENT THE REAL AMPS!!!! Especially if your a metal band!!
Just focus on the basics, use the mic FAQ and you should have alot of fun. Look for articles like this one:
http://www.itrstudio.com/4-track.html
Don't feel like you MUST rent compressors/EQ/Effects etc. etc. for this to work. If you go the all-in-one multitracker route, you can always save all your tracks when your done, then use your PC to do all that stuff.
Good luck