Car stalls w/o any warning? Does it idle funny in park? Any noises from it?
I'd say start off with the freebies. Check all battery connections at both ends, look for corrosion of any sort and any wiring that might be bad.
Then move your search up to the coils and ICM, any cracks or burnt posts.
From there a tune up may be in order... pull some plugs and see how they look at the least.
Since you just bought the car, the throttle body could use a good cleaning. Pull it off, remove and clean all sensors and the throttle body itself.
Let us know once you have completed these steps and if you've had any luck or discoveries.
00 Regal GS: All kinds of cool stuff.