good choice dude! layne was one of the all time great grunge rock vocalists so if uve never sung you may have your work cut out. First step is type "Brett Manning" into youtube and watch all his videos on warming up and about the anatomy of the voice so you know what your dealing with.
Then to get that layne staley grit, check out on youtube "jamie vendera discusses vocal grit".
To learn range you need to learn some vocal scales which are also available...on youtube!
Singing Success by brett manning is expensive but well worth the money if you are taking this seriosuly, otherwise for £15 you can get Raise your Voice by Jamie Vendera which is a cheap way to get you well on the right track, good luck bro.
Adam