Hello 68, welcome to the truck stop.
One thing comes to mind, was the MH tires placed against a curbing before it was put into park ? If it was rolled into a curbing, blocks or some such, then pushed into park while there is still pressure against the wheels, that would cause it to be very hard to get it out of park.
If such is the case, block front and back of front tires so the MH cant roll, jack up just one rear tire and that will relieve the pressure.
This scenario can happen if it is parked on a hill too.
I imagine that this is a cable shift. Block front and back of all wheels, disconnect the shift cable from the transmission shift lever and see if the shift lever will then move out of park.
Thats a start.