If you can wait a few weeks, please do as there are so many raging rumors of the iPad 2. No point in jumping the gun if you can avoid it.
That being said, buy the most iPad you can afford. You'll appreciate the extra memory and 3G later, even if you don't think you'll need it day one.
As for a case, you'll want something that fits your activity lifestyle. I've gone with just the Zagg skin and a 10" laptop bag, as I use the keyboard-dock all day long. My wife is more mobile with our son and uses the ZooGue case all day long.
Piko