Rootings very easy. I would highly recommend
this rom. If you updated your phone you're already familiar with the
updater (if not, here's a link). All you need to do is replace the .tar file in C:\Program Files\Samsung Electronics\SWUpgrade with the
downloaded .tar file then run the updater. After the updater has done its thing and the phone has rebooted, follow the directions in noobnl's thread (first link) to put the phone in recovery and flash his rom. The first flash via the updater will wipe your phone, but subsiquent updates via recovery won't. If you want to back up your programs and data before the install, you can find advice around here. Personaly, I bite the bullet and reinstall everything from scratch. There's a free program called App Dragon in the market that will email you a list of all your installed programs for easy reinstall if you like.
noobnl's rom already contains some froyo (2.2) files and is significantly faster than the stock 2.1 you're running now.