Ok, the guy towing my trailer has asked about the wheel bearings so I need to check them. Ive taken the wheels off before but what then? How can I test the brake lights without a car? I can get 12 from the house, but is there any way?
Toaster as mopar1973man showed in the link to the proper wiring of the 7 way rv plug the center is NOT ground. in your picture it is upside down from the graphic in the link. what I did was to print the graphic and took it out to the trailer with me and then checked the lights that way.
As for the wheel bearings the link that eliallen provided is perfect. very well written step by step. just remember that with wheel bearing CLEAN is very important. the smallest bit of grit will cause a lot of damage.
and While you have the drum apart you will also want to clean and adjust the brakes or at least check them to make sure they are OK as well.
One question I do have is how old is your trailer? and how far do you tow it?
I have heard that 20000 miles or once a year to repack bearings is the normal thing.
I would also guess from your statement that the fellow that is going to tow your rig doesn't want any problems when he is pulling it and if YOU check and OK the bearings he gets out from any liability if something does go wrong.
I would also add one piece of advise if you don't feel comfortable with following all the steps outlined in the link then see about calling a mobile RV or even a regular mechanic that will go to the trailer and repack the bearings. with all the right tools and experience the job only takes about an hour or two to complete.