Don't buy RAM or hard drive upgrades from Apple. They are grossly overpriced. The 16GB memory upgrade from Apple ($1775) can be bought here for $500
http://eshop.macsales.com/shop/memory/Mac-Pro-Memory#1333-memory
The stuff is so easy to install, especially in the Mac Pro, you pop open the side, attach the hard drive to one of the bay brackets and slide it in. RAM is just as easy, you pop out the cards, pop in the new RAM, put it back in.
That machine should easily last you 4 years if not longer.
