ed,
in all honesty, 80% of the problems with laptops, is improperly seated boards, or screws (most screws are ground screws), so put it back together make sure everything is tight.. make sure all screws are in place (look for ones that connect to the metal "shell" around the computer boards, those are the most important)
by it not booting, sounds more like a battery problem, either the batteries arent holding a change, or the charge they do have isnt getting to the computer itself.. therefor, try starting it up with batteries in and pluged in to a outlet.. if that doesnt work.. then try taking batteries out and pluging into outlet, im not REALLY familar with ibms.. but they cant be THAT much different then all the dell/toshiba/gateway ive worked on..