I agree, the stove is a fairly easy item to remove. The top of the stove should lift off and expose the LP line. loosen that up and find the appropriate screws to remove that hold it in. Viola! it lifts right out. I think it took me about 5 minutes to get the stove situated in place, LP attached and 4 screws to hold it in place when I put the new one in my unit.
Your old furnace should remove fairly easy. On the outside of the RV, remove the vents for the furnace. Then come on the inside and remove the access panel. There should be a few screws holding it to the floor/platform, remove them. Assuming you have already removed ducts, LP, and wiring, the old furnace should just pull out.
Are you scrapping your old furnace? If so I have a few parts that I could use.