The logic board should have letters on one side and numbers on another, so you can identify regions of the board by the intersection of the two. The locations I gave below should correspond to this grid system.

One non-destructive test you can do for the memory is to just overlay a suspect RAM chip with a known good one. Just be sure to get the correct orientation. Just piggyback the good one on the suspect chip, and see if that makes a difference. It's not quite the same as replacing the chip. If putting the good one on the bad one works, you know the bad one really is bad. If putting the good one on the bad one doesn't work, it doesn't really tell you much. But at least it is non-destructive.