Logic Board crash and 3 beeps on start up

A few months ago, I spilled some water on my MBP. Took it to Apple and they said that the water damage was confined to the logic board, magsafe adapter, and battery. Roughly $700 to fix it. Ouch. So I got the parts (battery and magsafe from iFixIt, stupidly got a used logic board elsewhere) and did the repair myself. It started working just fine for a while, but then I got a few kernel panic crashes (which have stopped happening now), but now it's artifacting across the screen with multicolored rectangles, crashing, then doing the Three Beeps of Doom. The artifacting tells me it's GPU and the place I got the logic board from refused to give me a refund. Still kicking myself over that. But the Three Beeps seems like a RAM issue. Should I replace the RAM first since I haven't done that yet?