you can drive it a while and it stalls out

When it doesn't start, check to see if it is getting spark and fuel to the ehgine. One will be missing. Identify which is missing so we can focus on that circuit.

The ignition control module they use has a tendency to fail. It generally starts and runs well until it is warm then dies, and will not start again until cool. Sometimes it is intermittent, or even only on hot days. Not exactly an expert, but I've been around the block a free times, and past quite a few 90's model Gm's broken down like this along the way. Try it in neutral unsteady of park first, the torque converter clutch solenoid and vehicle speed sensors cause trouble as well, and it may just eliminate a lot of searching. Also, though carefully, pour sim icewater on the crank position sensor after the car dies, if she starts you know where your fault is, make sure to check associated wiring in the area as well.