Yes there is an outside, and an inside bearing in each hub. The seals arent anything special. Got mine at a napa, after I got them out and could see a number on them. I know the doing this job sucks. Its not fun, and its messy to do.... but having the hub lock up and even fall off in the middle of no where wouldnt be keen either.
I run an after market TPMS system on my trailer tires too, that way I can see the PSI, and the temps, in case a bearing does start to go south. When I had my first new fiver, the dealer had greased the hubs before I took delivery. Being a newbe I wasnt sure how anything worked for a while. Year later I decided to check my brakes, cause they didnt work hardly at all.... and found there was about a tub of grease pumped into the brake area inside the drums. Blew right past the seals big time. Had to buy all new brake assemblies cause you cant de-grease the brake shoes once they are slimed.