New guy with ?'s

Hey, my name's Tim and I just bought a '95 Sierra Z71 reg cab, short bed with 92,000 miles. It is in good shape, but it seems to stumble off idle and it shifts kind of hard into 2nd (700r4). I have'nt had a chance to tear into it yet, but I will be soon. Any advice or problem areas I should know about? It's a 5.7 and I want to keep it pretty stock, just maybe some drivability upgrades. Does anybody know if the GU axle code is 2:73 gears? Also the dome/cargo/3rd brake light doesn't work. I checked the fuse and the bulbs but to no avail, oddly enough, the two switched lights on either side of the dome work..... Sorry about all the ?'s, Ijust want to get rid of the niggling bugs.

try a good induction cleaning....fuel system cleaner to tank full of gas...that engine may still have a timing adjustment you can check
need the third digit for axle code GU_ ?
make sure dome-third brake lamp socket and/or connectors are corroded

Sorry, it's GU6. Thanks.

3.42 ratio..no problem