I did this mod to my NES, although since I couldn't find the SCART cable I just used S-video and it looked FANTASTIC.

a couple things:

1) get a desoldering gun.

2) add fresh solder to the pins holding the PPU in place. this gives you better flow.

3) there's a few pins that are very hard to remove for reason I can't exactly remember. you basically have to just add solder, suck it off, etc

4) wiggle the pins around, this will usually free them

once the old PPU is off, the rest is pretty easy. I didn't have a drill so I just left the top off, otherwise you can drill a hole for the S-video out/ RGB out and glue it onto the plastic.

it really does look amazing but it might not be for everyone. the picture is very sharp, so if you have a framemeister, it's not a bad idea to zoom out on the picture so that your eyes don't bleed.