It took me about 5 hours alone and a lot of that was cleaning all the oil and dirt from the case. You will need a puller to remove the t case from the output shaft. I have read that some have luck with it coming off easy, not in my experience. Also be careful when reinstalling, the rear output...
Have you pulled the bulb out and looked at it? I would start there, and check the socket for corrosion. Don't over analyze and assume it is some complex issue. Start simple.
I installed roundeyes on mine, very happ with them. Make sure you install a relay kit, your not going to get as much a difference with the headlights being fed through the stock wiring.
It looks like you are missing your 12v supply wire. That would go onto the lower terminal, below the loop for the regulator. I would try running a fused 12v feed to that terminal and you should be good to go.
I hate to be the a**hole and use hindsight, but if you would have done leak- down test you could have eliminated several things and may even of found the fault. Where the ring gaps lined up? What are the conditions of the valve face and seats? Does the head gasket look evenly compressed across...
edwjmcgrath is right, this is where you need to start. Don't start replacing components to see if it corrects the fault. If you do find a short then make your way down the complete circuit. If your wires run inside the steering column(cover) may be a good place to visually inspect because it is...
Don't condemn the PCM to quickly, I have burned myself many a times by not exhausting all other possible issues. I recall vaguely working on a buddies blazer that was having fuel pressure issues and it ended up being the FPR. I am not saying that is your exact problem but it is worth some diagnosis.