Trailer wheel bearings are older technology and the design has been around for decades (My 1964 MGB has the same style bearings).
You don't have to take it to an RV dealer as any good auto mechanic should be able to inspect/repack/replace these kinds of bearings and you don't need any special tools.
Heck I've done it on my driveway many times - it can get messy but it's really simple. Driving out the old races can get a bit tricky if you don't know what you are looking at.
You can also google "trailer services" in your area - they should be able to help you as well.
BTW - adjust the brakes while you're there...