I had a 89 Pace Arrow. I made the mod. Very easy to do. Been a long time ago. There is a large switch in a kitchen cupboard to switch from front to rear A/C. I bought anther switch like it. I mounted the new swich near the generator. That was where the power came in. I wired in the switch so you could select generator or shore power. At that time RV parks were 30 amp. The second cord I wired in plugged into 20 amps. It was a very common mod back in 89.
BTW the second wire I wired in had a 30 amp plug so was heavy duty. I used a 30 to 20 adapter on it.