I have to agree with OC because changes are made. Other thing you can do is get under the camper and get the information from the axle tag and then jump online and get the parts diagrams from the manufacturer. If you have a serial numbered axle, a call into them and they can tell you exactly what it has.
As for getting the replacements, IF you have a trailer dealer/fabricator/parts shop nearby, head straight to them versus an regular auto parts store. They will have everything you need in-stock. There really aren't that many styles of seals and bearing sets used in trailer axles. It's the inboard and outboard combinations that switch up. If you are a long-hauler, I suggest getting at least a pair of extra seals and a complete set of bearings for one hub. Pre-pack them and seal in a ziploc bag after you take out as much air as you can. Trust me, this can save a trip!
EDIT: Dang, I type too slow because all those above answered while I was typing!