The dealer told me the same thing when I wanted to get an extra key fob. I bought a new one off Ebay for less than the dealer wanted, looked up the instructions, and programmed it myself.
Here's the instructions from the link in my previous post:
PROGRAMMING
2001-2003 Pontiac Grand Prix
+++ Do this in order to replace or add a transmitter or when your system malfunctions
1. Remove key from ignition
2. Remove the MALL PGM fuse, from fuse box.
3. Close doors
4. Turn your ignition to ACC position.
5. within 1 second… turn ignition to OFF, then back to ACC
6. Open & close driver’s door, the system will sound a chime to let you know you are in active programming mode.
7. Now… you need to HOLD the LOCK & UNLOCK buttons on your remote until the chime sounds, for about 15 seconds.
8. Repeat #7 for each remote to be programmed ( Maximum of 4)
9. Remove key from ignition.
10.Refit MALL PGM fuse
11.NOTE - existing remote memories will be overwritten
12. Obtain and reprogram all any existing remotes
13.Additional feedback settings can be set to respond to the remotes.
Note: a maximum of 4 key fobs can be programmed on these vehicles
^^^I wouldn't pay the dealer $60 to do that..