Thanks so much Snarf! I started on this immediately after finishing "Don't Stop Believin'," so it took a little less than a month, practicing 2 hours a day almost every day. I start learning the lead at 50% tempo (or even 30% for the really fast parts) to get it under my fingers, and play though it a whole bunch of times until I can remember the timing of everything - then I can switch from playing along with the original song to playing along with the backing track (so I don't have the original guitarist to cover up my mistakes). Slowing the tempo way down is also very helpful for figuring out where the tab is wrong. Then I just start moving the tempo up a little at a time and after a few weeks, get it up to full tempo. Somewhere along the line I eventually get it memorized too
For the rhythm guitar and bass I might have started at 80% tempo as they're not nearly so technical. I still had to play through the bass part probably 15 times to get a good take where I didn't forget where I was during the choruses, as they're all a little different. And the lead took many, many takes lol.