Mr B.
if it's the video card, it's embedded onto the mainboard of the unit, and would require a replacement of the mainboard itself. Brand new, it would be probably more than the new unit you're getting, however there are places that sell "used" mainboards for reasonable prices, then the task would be to actually disassemble the unit, and replace the board.
Ebay does have them, as well as other internet vendors that specialize in taking units that have been discarded, pulling the usable parts out of them and selling them. A google search will bring up several dozens (hundreds?) of sites.