Hello, I wish you luck in getting your SA-7 player repaired. The SA 7 player is several years out of production, so it is indeed likely that the laser assembly, known as SACD-M1, might be out of stock in the Marantz supply of parts. It's just that this assembly is based on the HOP1200 laser, which is available and cheap as it is still in production. The big issue is finding someone who can fit the laser into the assembly and make it work again. I do not know how difficult this is, but I think it is the main reason that Marantz Service Centers replace the whole assembly. Although it could be just because it is easier to do it that way.
If you have to send your player to Canada it will be very expensive. Although to replace the SA-7 with similar quality and featured player would be way more expensive.
All the best, Steve