Probably a stupid question (1992 Regal)

I have a 1992 buick regal custom. I need to replace the engine. It is the 3800 engine, btw. I found a pretty good deal on a 1999 Regal GS engine/transmission combo. Is it compatible? If not, what are the necessary workarounds to get it in the car and running? I'm assuming the ecm's are different and will need to be part of my purchase. Please help!