The remotes and the module are set at the factory. You can't replace it. Do you have the remote? Hope so. Maybe it just needs a new battery?
Maybe you have the later potato shaped remote and not the square one? If so then you can reset the fob:
Note: This process must be carried out in 8 seconds to access learn mode. Best done with two people. You should have both remotes available or the second one will not work.
Open hood and have assistant hold hood alarm switch down.
With all doors closed and lock knobs up turn the ignition key on then off.
Cycle drivers door button down then up.
Assistant should then release the hood switch.
Turn ignition on then off.
If done correctly, horn will beep once and dash LED will light up. This indicates the learn mode has been accessed. If this doesn't happen repeat 1 thru 6.
From inside car push and hold first remote. The dash LED should flash 8 cycles a second for one second, indicating that the code was received. If this does not happen repeat steps 1 thru 6 again.
Push and hold the second remote if the code is received the dash LED will flash 8 cycles indicating that the code was received. If this does not happen repeat 1 thru 7 again.
Note: Turning the ignition on at any time will cancel the learning process.
The system can only store two remote codes and must be done one at a time.
If you only have one remote, program it twice.
PS there are a bunch on Ebay for about $70. Still way too much, but hey....
1966 109 5 door wagon 300Tdi "spermaceti fueled"
1994 RRC LeWiB "ruining the air behind me"
All my troubles are Rover