Purchase only one chip from logic board
I have two MacBooks (namely MB466 and MB990), both died of spill, and the problematic part in each of them is NVidia's MCP79MXT-B3 chip, which requires replacement.
So is it possible to purchase only this chip from you?
Hi! I don't work for iFixit, but I can say that no, the chips themselves are not available individually, and they are generally purchased as part of a new logic board. There may be specialty outlets which offer the raw chip, but I haven't heard of any, and even if they were available, replacement of that chip requires expensive equipment and technical expertise.
I'm curious, how do you know that the video chips are specifically the problem? Have you tried connecting the laptops to an external display? There is a common video chip flaw with many Pros, and Apple will often swap the logic board free of charge if this is the case, so if by chance there was not a liquid spill (as Apple absolutely won't cover a liquid-damaged machine) and the machines do have the GPU flaw, it's worth taking them into an Apple store to see if they are covered.