as tim said...you can make it bolt up just fine...but getting it to run is a different story. you are going to want the whole wiring harness from the other car...along with the PCM, probably even want the transmission also. (dont recall if the 3.1 came with the 4T65E or the 4T60E)
edit: what is wrong with the 2000? with all the work and money that is involved in the swap...I'm wondering if you should just fix the 2000 with parts from yours