Sun Valley in CA seems to have good marks from those on this list and way less than 5K.

One of the issues with the 5 K pricing is if a shop does not rebuild many MB trans of this model, they can't offer a blanket price. When any part is rebuilt in volume, the easy rebuilds subsidize the completely destroyed units.

A shop that builds a low volume unit has 2 choices, give the customer a high price to cover a completely destroyed unit ( causing them to run away " That is too much $ " ) or give them a low price then add to it ( " You are just getting me in the door then selling me stuff I don't need " ) With the former they don't get the job but with the latter, they get the job. Given a trans rebuild isn't common, the latter has little risk because the customer isn't likely to come back even if they were treated well.

The R&R at a typical shop should be ~ $ 500. However the R & R must be negotiated before any work is done. Be sure to provide a very detailed description of what work you want done and expectations to avoid future problems. Details like throttle valve cable and vacuum modulator adjustment are critical to trans life.

Typically better shops don't want to install bought parts due to a wrong part tying up a bay , shop being blamed if the part fails and loss of profit on bought parts.

Do you have a good relationship with any general repair shops? A non transmission shop can change this especially if they change engines.