Richard, the good news is rebuilt motors are readily available through a well sourced NA parts store. The call up I used is for a ‘69 Chevelle front window lifts. The same basic Delco motor assembly is used in a wide variety of sixties seventies GM products.
The wrinkle is the right side Chevelle or equivalent motor is mounted on the left side in the Plus 2, and vice versa.
The parts store will generally require a core. Make sure you remove the mounts and regulators to re-use with the new rebuild motor.
Here is a thread with more details on the Cardone part numbers and the removal process
viewtopic.php?f=13&t=24949&start=I also rewired the doors and used relays so that the rather old and delicate dash switches only see relay trigger loads. Agree with others you may want to do this first. I figured properly rebuilt motors were pretty reasonable though; in my case they made an enormous difference evan after all the other repairs and mods. The in and out procedure is enough of a job that I figured a fully rebuilt motor was great value. Perhaps one of the rare cases where we have an easier time sourcing rebuilt motors this side of the pond.
Note when looking in the archives the Elan uses a completely different window lift system than your Plus 2, which can be a bit confusing.
HTH