3.4L to 3.1L engine swap?

My mother has a 96 Lumina with the 3.4L. The engine has been a problem for years. I never quite worked right despite multiple service station visits. It seems that the engine has finally gone after only 65,000 miles. I'm interested in replacing it, but I would like to get away from the 3.4 due to bad experiences. I would like to know if anybody has done this before and what in all it would require. I've swaped engines in other vehicles, but always with the same engine. Would the existing computer need to be replaced, or would it work with the 3.1? Is there anything else that should be considered, or is it more trouble than its even worth? Thanks for any help you guys can give.

Mike

Computer would need to be replaced. The wiring harness would also have to be replaced. I'm not sure about the trans. I think everything had been changed over to 4T60Es by then.

You could find a 3100 (not 3.1) motor from a 96/97 Lumina/Grand Prix to swap into it.

I wouldn't bother with the 3.1, when a 3.8 will give you better performance and bullet-proof reliability. Lumnas came with the 3.8 as an option the last couple of years that they were made.