... my question now is how much can a shop true up a wheel through spoke adjustment?
There's really no telling. If it's all down to spoke tension being off, then just about any rim can be saved.
Trouble is, wheels usually end up untrue as a combo of spoke tension + rim damage. And even something like 1/2" of sideways throw by rim damage is really hard to save through trueing alone - spoke tensions become too different for the wheel to be reliable.