[Richard]

Having done this twice (two diff coaches), there are some challenges. If you have two pipes out the roof, then it is easier. One is a little trickier since the AH and the gennie join in a custom welded right angle.

If possible find a location where there is a dip below the exhaust pipe. If not put it up on ramps. You want to be able to lower the pipe out of it's vertical chase.

There is a pipe union at the exit of the AH the mates the 2 inch pipe on one side of the union to exhaust pipe on the other. If you cannot break the union loose, take a side grinder and split the union nut in two pieces. When you run new exhaust pipe, you will need to weld the new pipe union on the exhaust pipe. Don't forget the nut.

On the other end, being able to drop the vertical pipe down a foot will help tremendously in fitting up the new exhaust section. You may or may not need a new elbow.