Alright, first it's obvious that your shop's guessing as they just throwing parts at it.
Would I then trust them to replace my $2400 trans (parts and labor) or even assume that their guess at this point is correct? No way!

Both codes relate to the vehicle speed sensor signal being absent SO that's the first thing that should be looked into with more detail, like actually fault trace the wiring from the speed sensor to the ECU using a break-out box and a Volvo dealer has a specific tool for that job.
As it is, if that circuit or the trans ECU is the problem (not the trans), then if you OK the trans replacement it'll all be a complete waste of money.

Get a second opinion and preferably from a dealer, AND request that a master tech look at the problem when talking to the service writer.