In regards to the power jack, refer to your owner's manual. I've used a spray on dry lube on mine and that was the jack I had on the trailer we just traded in and the jack was still working well after 10 years with just one repair to replace the power switch.
For removing decals, use a hair dryier or heat gun, a plastic putty knife and WD40. Heat up the decal until you can start peeling it off. Once peeled off, spray on WD-40 to remove any adhesive residue. Please note that I used this procedure on a trailer with aluminum siding. So, you may want to see what others have done when dealing with fiberglass or laminated walls.