I am actually "upgrading" an old pc but I'm basically only using the parts mentioned above from it. Which means I'm putting in a new motherboard, replacing ram, gpu, and cpu. I do have a few concerns about the upgrade (listed after upgraded parts)
You will need a better psu for the video card alone. DDR3 ram is relatively inexpensive. And 8 gigs will get you buy with no problems 4 gigs is also sufficient if need be. Most cpu's have their recommended ram listed a good way to check a build is to use http://pcpartpicker.com/ this way you can play with it and adjust your budget accordingly.
The psu is the heart and sole of a system without it no component will work or work correctly. And when pc's run into problems the psu is usually the prime suspect. Just some thing to keep in mind to make sure you get a decent psu that will power your system and be reliable. I did the same thing recently :
I chose AMD as it was cheaper and the am3+ board left me room for a better cpu when finances allowed it. That was the path i took. But i also already had an Antec VP450 i had just bought to replace my old psu so i did not have that expense though i had to buy a ide to sata converter to use my old hdd as the new board did not have a ide hook up. Not sure about your hdd but some thing else to keep in mind as well.