...bummer. I'd be unhappy with the longevity of that re-build.

 

Now..Just throwing an idea here.You said , you can't shift a tranny out of P. There is a RF capacitor down there , attached to the transmission case, directly behind a shifter cable mechanism, it's a little black box with a wiring harness. When this unit fails , transmission does not respond and you would not be able to shift it out of Park.
I would try replacing this little transmission capacitor first, it is a cheap part after all, and start from there.
Supposedly you can also try to just disconnect it and try to drive away.Cheers