I plan to upgrade hardware one piece at a time. When I swap the motherboard, will my 8800 GT with pci-e 16x slide into the pci-e 2.0 16x slot on the new mb?
One more thing, will my old gpu be better than on-board graphics in case I go that route?
Yes, as long as the motherboard you install has a PCI-E 16 slot, you will be able to use that 8800GT as it is backward compatible. Currently there are no integrated graphics solutions that are better than an 8800 GT.