I might be wrong here, but...
I wouldn't mess with the valve body, or at least I would leave all the springs and valves *in* the valve body (ditto for accumulators). The springs and perhaps some other parts are what make the transmission unique to your vehicle, so leave them as is; let the rebuilder monkey with the valve body, as necessary.
Otherwise, it would be interesting to open up the trans and see what's broken, but, if so, replacement parts are readily available. In other words, I would leave the decision for "rebuildable /not rebuildable" to the rebuilder.
Now, having shown my ignorance, let's see what others have to say. Where's
@tayto?