I looked through my bookmarks for the site from where I got my instructions, but it isn't there anymore. Looks like it was on an educational site, so it may have been a student's page that got shut down. Unfortunately, I didn't save the instructions locally.
The composite mod I did is incredibly easy to do. I just don't know what points to tell you to solder to without having my Genesis open.
Edit:
Seems like everyone does videos now instead of just writing text tutorials with pics. Unfortunately, most seem to like to talk a lot before they get to the actual mod.
Anyway, I pulled some pics from one of these videos. The pics show the pinout for the DIN along with wires soldered onto the bottom of the motherboard. The problem is that I believe this person is working on a Mega Drive, even though the video said it was for a Genesis. The reason I mention this is that the board looks a little different from mine.
As for the audio, you probably know you need to solder to the headphone jack for stereo. Before I go into this, note that I am doing this from memory (just had my Genesis apart a few days ago). If you lift up the headphone jack, you should see the points where it attaches to the board numbered 1, 2, and 3. I believe one is ground, two is right, and three is left. I would verify this prior to making your connections, though.
I don't know if this helps at all, but this is the best I can do tonight.
Edited by YAGRS, Tue May 31, 2011 8:17 PM.