1. Your old rear derailleur will not work with brifters; if you stick with Campy brifters, they seem to work with just about any front derailleur (try your old one before you buy a new one).
2. Assuming you are sticking with Campy, I'd recommend Mavic Open Pro rims or Aeroheads, laced to the Campy hubs of your choice.
3. Standard (non-compact) cranks most commonly come in 53-39 these days. Crankarm lengths between 170 and 175 are easily available; longer and shorter are out there, but harder to find.
4. Qbike.com is a good place to shop for gruppo prices. There shouldn't be anything wrong with your old stem and bars, assuming the frame you bought has a threaded fork.