The motors are identical to the ones on the jacks. I bought a spare motor, however I am not sure that I will ever use it. A spare jack may be more useful.
We have not had a motor fail. In our case the weld between fitting at the end of the screw which is like the one on the top of the outside jack broke at end of the screw. This fitting was welded onto the screw. A person dear to my heart, had a habit of bumping the motor one more time after it had reached the stop, and did so one time too many when going up and the weld broke. I removed the parts, took them to my professional welder (I weld but still use a pro for a lot of things.) and he did a good job of tig welding the fitting to the screw. Cost $20.
I think that the assembly is pretty stout and will last a long time if it is not abused repeatedly. We have about 100# on the roof, no A/C, two solar panels and a Thule box.
With the fitting broken loose from the screw, it was quite easy to raise and lower the roof. If the motor is connected, its much more difficult to raise and lower the roof. You are right in that a jack motor could be swapped for the broken lift motor and be done with the difficult part of the job and use a crank for the one jack until repaird.
With the tools I carry I could do the job on the road. I carry a small tool bag with the usual hand tools and most of time an electric drill. Electric tools would make the job much, much easier.
No worries, lets go camping.
Rick