Confused 99 Sierra 2500 wont start

[Jakeofall]

Hello all, OK I've got a 99 2500 , it will crank. Intially I had a dead battery. After I put a rebuilt starter and new battery on it. I don't have spark on the plugs and the OBD port is dead (OTC Genysis won't communicate). Also the Indicator for the gear selection does not show up. The instrument cluster seems to be functioning except for the gear selection indicator, The P-R-N-D-1-2 letters show up just not the block around the letters. It would seem possible that the computer has failed. If the computer's OBD was active then i'd start looking at the transmission sensor that indicates position. Anyone see anything like this before. Also Can a computer from a 99 4WD 2500 work in a 99 2WD 2500 with the same motor (6.0)? Any one have any Ideas?