I just finished this job, also with the same furnace. It is possible to do it without removing the furnace from the RV, which is the way I did it. If removing the furnace is a simple job for you, it will make the motor replacement easy. If removing the furnace will be nasty, this is roughly the order in which I recall having to do things.
1. Disconnect the fuse to the furnace and turn off the gas.
2. Open the inner and outer furnace doors. I drilled out the rivets holding the inner plastic door on because it got in the way. I replaced them with stainless steel sheet metal screws when I was done.
3. Disconnect the ignitor wire and harness from the circuit board on the left, then unscrew the circuit board's wing nut and put the board in a safe place.
4. Remove the four 1/4 inch head screws that hold on the curved plastic motor cover. Move the wires aside and carefully move the cover aside. You may need to hang it up with a wire tie or something.
5. Remove the screws that hold in the exhaust pipe, on the right. Pull it out with a good yank. This is necessary for step 8.
6. Remove the screw that clamps the motor in place.
7. With a long 1/8 inch allen wrench, loosen the set screw on the steel squirrel cage exhaust fan and the clamp screw on the plastic blower fan. (The motor has shafts on both ends. )
8. Remove the screws that cover the steel squirrel cage exhaust fan, then carefully wrestle with the cover and bend it enough to remove the steel fan. (Be sure to put anti-seize in the hub when you replace it!)
9. Remove the plastic blower fan. (Yours may be metal. ) This is where removing the circuit board will have been useful.
10. Carefully wrestle the motor out to the left. Cut the two wires, one red and one black, leaving enough to splice in your new motor. The new motor should have spade plugs already installed, however.
11. This is the step in which I say that I probably omitted a step or two, for which I apologize. I also have to say that if you wear gloves in size XL, this is going to be a pain in the behind.
Special Tools: You will need a good 1/4 inch drive socket set with a swivel adapter and a couple of extensions. By a "good" set I mean one where the noses of the sockets taper and are thin-wall and six point. I suggest a t-handle allen wrench set. A retrieving magnet will also be useful. You'll need some time and patience.
Installation is the reverse of removal, as they say in all the cheapo car repair manuals. Be sure to buy some thin stick-on foam rubber. You will need a piece about four inches square to replace the one where the motor abuts the exhaust fan housing. Tghat serves two purposes. (1) it helps prevent burned gas from entering the RV, and (2) it prevents rattles. The Atwood design is *very good* about preventing burned gas entry, so the foam rubber is mostly for rattle prevention. I used foam camper cap tape.
Be sure to test-spin the motor as you reinstall the squirrel cage fans to ensure that they don't interfere with their covers or rub on the ends of their housings. I used anti-sieze on both of the motor shafts, just in case.
When you clamp the new motor in, it is altogether too easy to clamp the two white wires into the metal parts that hold the motor in. Be very careful to avoid this! It is a mistake that I made, and I had to do the job all over again. If either of the white wires get pinched, the job will seem OK for quite a while until vibration wears through the insulation. Then all will seem normal when the thermostat turns on the furnace until the fan turns on. At that point, the fuse will blow. It is a difficult problem to track down. For me, it was self-inflicted.
If you run into problems, send me a PM and we can commiserate.
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