3800 Series 2 engine swap?

I have an 02 Pontiac Grand Prix GT with 124,000 that came standard with this 3800 series 2 engine. Very reliable. I found a Base model 2013 Impala with 120,000 miles. But the 3.6l is garbage. And in addition, I found a duplicate 02 Grand prix with a bad transmission, but with the same good motor with 160,000. My plan was to finish and sell the car and move up to the latest w-body I can afford. I was told I can make the 3.8l work with the car's computer and wiring and stuff, but I know I would have to switch to the car's flex plate so it can happily bolt up to its 6-speed transmission. But that's pretty much all I can think of.