It is pretty easy to do it yourself. You can get the parts from Wrangler Trailers near downtown Mesa on Lewis or you can drop the trailer off and let them do the work. They do quality work at a decent price.
I was hoping for a procedure. This is exactly what I needed. Thank You!!!!Do you have a service manual for your hubs? Have you been greasing them when you go out? I'd jack up one wheel and see if you can rock the wheel in and out by holding the top and bottom of the wheel pushing the bottom in and pulling the top out, then push and pull the opposite way. Then do the same for the other wheel.
This PDF file might not be exactly what your trailer has but it is some good information on hub maintenance.
http://www.ufpnet.com/Portals/0/PDFs/Bearing Lube Axle Maintenance.pdf
Here is an insert out of that PDF on a hub that is simular to your system, might even be the same.
BEARING ADJUSTMENT
Wheel bearings have been precisely torque set at the factory. To maximize
bearing life, we suggest you check bearing adjustment every 2 or 3
years.
Jack up one side of the trailer. Grip the edge of the tire on both sides
and try to rock or move it. If you can move the outer edge of the wheel
more than 1/8" (end play), remove the dust cap, the cotter pin and spindle
nut retainer.
Tighten the spindle nut to 18-24 inch pounds, which is slightly
more than "finger tight". Don't over-tighten. When the nut is positioned
properly the wheel should turn easily and there should be no end play
(lateral movement) of the hub with respect to the spindle.
To replace the nut retainer, find a position where it will fit over the
spindle nut so that the cotter pin can be inserted without having to loosen
or tighten the nut. Insert a new cotter pin. Recheck end play. Spread the
ends of the cotter pin to keep it in place. Add grease as necessary and
replace the dust cap.
If you need maintenece I believe it was Jackson's Trailers out in East Mesa that does work on them.