Haven't had the experience directly but there have been a couple of posting in the past concerning owners who did it themselves or paid for the work. Crate motors are available but the labor is the cost driver. You're going to have to make a hard decision considering the cost to repair could be higher then the value of the coach.
Engine can come out two, maybe three directions. Out the top thru the dog house, out the bottom or out the front. Each has advantages and disadvantages.
Going up thru the dog house may require a some disassembly of both engines such as removing the heads to fit the opening in the coach floor. There is also the problem of getting access with a lifting rig inside the coach.
Going down might be a bit easier but will require removing the front axle and also lifting the coach to get the engine out from under it once removed.
Going out the front will depend on if the front cap design will allow and how much can be removed without cutting.
Think happy thoughts and its just a failed head gasket or something equally simple that can be corrected with removal. Tell us what Ford finds.