As has happened with many of the projects we have undertaken, the removal of the air conditioner was not as easy as it should have been. The unit was supported by a frame constructed from 1" x 6" boards, and those boards were supported by virtually nothing. I removed the old boards and framed in a new structure that should keep the air conditioner from moving around.
With the AC unit out and the support structure in, we hung a sheet of drywall and secured the unit.

We only had the time to hang one more sheet of drywall before it was time to clean up and go home. I re-installed to propane gas shut-off and replaced the outlet cover.