Jeff the Toyota encyclopedia to the rescue!
Several people around the forums and that I know personally, have dyed their interior vinyl with great success. If you do a shitty job, it'll look like shit. Do a great job and it'll look great. What you put in you get out, I don't see how that isn't a bright idea.
Annoyingrob did the interior of one of his cars, looked great from what I saw.
I've seen plenty of "pros" do some really, really, really, REALLY shitty fucking work. Do your research and do it right, that way it's done right. If it's not, you have no one to blame but yourself.