HELP... "Chevy took a shit"

Okay last night my water pump went in my 89 Chevy CAvalier with a 2.8 Well stupid sensors....... my temp sensor died and i didnt think nothin of it just driving down the road and all of a sudden i started getting bad power loss and was trying to figure out why... well needless to say next i hear Knock Knock Knock Knock..... and i am thinking awe shit well the motor has taken a big ole shit and i have a nice ass 3.1 out of a 90 cutlass supreme good as new with only 121KMiles on it (barley broke in) so i am gonna set this motor in here along with the TH440 trans and am wondering Is it possible to reprogram this computer to make it work in here or is a computer from a 91 cavvy compatable or will the old computer self adjust i also have a 4-plug computer from this cutlass and am wondering if there is anything i can do to make this computer work? but anyway if anybody has any suggestions please reply i need some help ty

-Dave

As with any motor swap, you'll need the computer (ECU) and wiring harness from the donor motor. You will also have to find a way to mount the thing in there as the motor mounts are likely not compatible. I'm not sure about that though. Also, I don't think the gauge cluster will work with the new ECU.

Well i have been doing my homework and the only difference between the 2.8 and the 3.1 is the engine stroke and have found that the 2.8 computer should be compatable with the new 3.1 so here goes nothing and out of cuiousity will i have a problem making my shifter compatable with me 4th gear in the trans? i have only 1st 2nd and drive on my shifter i was wondering will i need to rig anything to get it to go as far as i will need it to to get to first gear? i have also been told it will work perfect because the transmission will engague differently then the 3 speed and that when i am between say 1st and 2nd it will acually be 2nd then 3rd will be third then 4th will be between drive and 3rd and i have also been told that park will possibly be like reverse and nreverse neutral and if this is true i am gonna have an issue but anyway any help will be appreciated, thank you

-Dave

HELP AGAIN!
Okay my transmission from my 91 cutlass has yet another difference from my cavalier The cavvy has a Square plug on the front my cutty has a round one how manny problms will this cause if i just leave it un connected? or is there a way i can splice it togeather?

-Dave