Thanks for the info guys, now which one of these is correct for my car, they are all listed as fitting 2000 GTP, I don't want to order the wrong one:
http://www.ebay.com/itm/4T65E-34T-DI...da1aac&vxp=mtr

http://www.ebay.com/itm/4T65E-38T-DI...9dd951&vxp=mtr

http://www.ebay.com/itm/4T65E-42T-DI...daa534&vxp=mtr


Here is the axle that oriles gave me:
Outboard Joint Type: Spline Nut SKU: STK:GM-8097
OB Spline Count: 33 Brand: SurTrack
OB Nut Size (mm): 33 Manufacturer Part Number: GM-8097
Number of Outboard Splines: 33 Number Of Inboard Splines: 39
UPC: 00844084030979
Measurement Type: Compressed
Thread Pitch (mm): 2 Location: Front Passenger
Overall Length (mm): 620 Length (mm): 620mm