Hey David, welcome to the DUC. My 2 cents(since I don't use Cubase) is this. Once you have learned ANY system, learning a new one will be a bit tougher as you have to break old habits(which you don't have when you start from scratch). As for tutorials, youtube is a great resource. Then there are some 3rd party videos like Pro Tools: Secrets of the Pros and Groove3.com. Just a google search of
Pro Tools training videos will turn up lots of options.
In any case, all the major DAW platforms will handle about anything you can imagine, so some of your decision will come down to collaboration needs(what do others use and do you share projects) and some maight be related to specific needs(like for instance; Logic Pro seems to do midi better than most, while Pro Tools seems to do audio better than most). Of course, some will insist that X is much better than Y, but its tough to be objective on this. I know Nuendo is a very capable program(according to some others), but after watching an experienced guy work it for an afternoon, there's no way I will give up PT for it. Having said that, every time I sit at a Cubase setup, I scratch my head and can't figure out the most simple things
Go figure
I must add, pro Tools seems to be more hardware-finicky than other platforms. Its quite easy to find your computer(especially a PC) isn't compatible. Sometimes its a simple as a new firewire card, other times, the entire motherboard isn't compatible. Homework will steer you best.