my brother just purchased a 97 gmc sierra 2wd with the 5.0 and it needs some minor work but i have a few questions.
it have two error codes for oxygen sensors one for bank 1 sensor 1 and one for bank 1 sensor 3. which sensors are these because i looked under the truck and i see one on the drivers side and then there are 2 on the passenger side before the cat.
the exhaust is also leaking where it joins to the manifolds is there alot of problems for that?
and the other question is he wants to put an aftermarket stereo in but the factory one says it have the theftlock, how do i know if this is on or how do i turn it off to put a new radio in?

thanks in advance