Yes the M3-2312 remotes were discontinued a couple of years ago. The new model is the 382 Digital Remote that we sell. The remote comes with a programming jumper and instructions for using the jumper. The jumper is used to transfer the code from a programmed remote to new remotes.
If you purchase the remote from us and don't have any other existing remotes then you will need programming instructions to program one remote into the opener. If you email us with a request for your particular model opener we can email you the instructions or you can find them in the Marantec opener manual.