Don't let these guys scare you. MSF is a GREAT way to introduce yourself to bikes but it's not 100% necessary. I taught myself how to ride on a KZ750 which is a pretty big and fast bike - at least it was when I got it. There were no Internet chat forums, I didn't read any books(though reading PROFICIENT MOTORCYCLING is a great idea), and I didn't even know anyone who rode. I never had an accident until I was on my third motorcycle. (If I knew then what I know now, I would've at least gotten a few books and probably taken MSF.)
Scooter experience DOES help. Mostly because you already realize that you're invisible and have already developed some of the vision and evasion skills you will need to sruvive in the road.
Countrary to what a prior poster opined, countersteering DOES apply to bicycles and scoots. It's basic physics that it does. If anyone here doesn't believe me, hop on a bicycle, get it going at a decent clip and push on the right handlebar - I guarantee that you will turn to the right. Same with a scoot. HOWEVER, given the MC-your body weight ratio and fork geometry, it will be a bit different so don't assume a MC will ride/turn JUST LIKE a scoot.
Here's a pretty good site that has some pointers and parking lot practice exercises that will help you out:
http://bcrider.com/startriding.html
Take it easy, practice A LOT in parking lots and you can do it if you're careful. Gearing up properly is of course a very good idea.
If possible, find someone who has riding experience to be your mentor. IF not, post your questions here and on other boards. Heck, even if you can find a mentor, it's a good idea to validate what they tell you on Internet forums.
Good luck and have (safe and cautious)fun.