Windows 7 64 bit BY A LONG SHOT.
32-bit operating systems are limited to under 4 gigs of ram, while 64 bit can take advantage of much more. Nowadays, the minimum is usually 4 gigs, with most people opting for 8GBs. If you can pick, definately go 64-bit.
Depends. If you want one now, get it now. If you can wait, wait for ivy bridge or LGA 2011 or Bulldozer. If it was me, I would wait as Bulldozer and Ivy bridge will probably blow the sandy bridge and Phenom II processors out of the water.