He didn't even answer my question. Nothing about why it was hot when I removed it.
Richard, I think he did answer...
As long as you have a PCI-e port on your board and use the auxiliary power adapter that comes with your 8800gt, then you should be fine. You should also note that your power supply needs to have at least 26amps on the +12v rail
The reason your card may have been hot was that it may not have been connected to the PSU via the necessary 26amps/+12v rail, and if not, it wasn't getting enough power to run the cooling fan at optimum level. Before taking it back I would first check this to see if that's the root of your problem.
I have a 8800GT and had the same/similar issue when I first started up mine - the screen would break up into horizontal lines and then I'd get a BSOD - so I reopened the case and connected the card to another power lead (was connected to the case fan lead which has less power) and voila, everything worked as it should.
Hope this helps... the 8800GT is a better/faster card than the 8600 by far and would suit your graphic (rendering, etc) needs much better.