Mentioning 'alumniconn' threw me; I've called those things 'King connectors' (after the Manufacturer).
Mentioning a trailer put me into high gear.
Let me be blunt: I've done this once, and once is plenty. I'll explain where the worries are in this minefield- and there are plenty!
Problem #1 is the wiring method. Not just that aluminum wire was used - but that the ground wire is undersized, the boxes are smaller than anything you'll see in a real house, and the cables run unprotected just under the panelling (no drywall).
This means that the ground wire will almost certainly break as soon as you pull the device out - and it will break at the crimp fitting in the back of the box. Doom on you.
It means that there's no room for devices AND pigtails. Larger devices, like GFCI's just won't fit. The connectors make the problem worse. Plan on using some "Wiremold" extension boxes.
Opening the walls is easy, but closing them up neatly is a challenge. Be CAREFULL! The wires run just under the panelling, through notches (not holes) in the half-size 'studs.' In the ceilings, you don't have even that much structure; the ceiling material can be best compared to a dry sponge, rather than any wood product you've ever seen.
Perhaps you need not use the special connectors; there are aluminum-rated switches and receptacles readily available, and the price isn't bad. For GFCI's, though, you're out of luck.
Actually, the REAL reason things are not working probably has little to do with the aluminum wire, and more to do with simple age. The trailer I rewired had dead shorts in two places: the insulating partitions in the control section of the oven had failed (letting the little wires in there short out), and a screw had penetrated a cable when they re-lined the shower stall.
After my experience, I concluded that mobile homes are designed to NOT be worked on, and instead to be disposed of as soon as something breaks.
Finally, it should be noted that States have begun to require special licenses to work on mobile homes, and your EC licence might not be enough. If your state has a "Mobile Home" division, chances are they have separate licensing.