If its an Atwood Hydro Flame it is easy to remove if you have access to the side or above. Which way is it installed? On the flat or vertical??
On my Clipper the two furnaces are installed upright.
Disconnect the wire harness plug on the top of furnace.
Shut off propane and light stove to relieve LPG pressure, shut off stove and disconnect the line on bottom of furnace.
From behind, disconnect the distribution vents.
With a power screwdriver, take out the screws holding in the furnace by bending the taps on the retainer ring.
Wiggle the furnace out.
Suggest you do a full service and inspection while you have it out.