Are there any upgrades I will have to consider with my desktop specs, when upgrading my GPU to a 8800 GTX?

First, find out how many watts your PSU is. If it is below 450, forget about it. Invest in a solid Power supply, and everything including cooling will run like a charm. Also, the 8800 is a PCI express card. Make sure your motherboard has a slot for this (I think the slot is white, but not sure)