I have a 2006 Boatmate single axle trailer with the 'Reliable' oil bath hubs. I'm somewhat new to these types of hubs and the maintenance required for them. I drive about 8 miles from my driveway to the lake and in that time my hubs become extremely hot. I keep the hubs full of 50 weight and haven't noticed any leaking or loss of oil. From what I understand these hubs are supposed to be fairly maintenance free as long as you keep the oil full, however the temp of the hubs has me a little worried that the bearings are going bad. My question is 3 fold:

1) Is it normal for these hubs to run hot or are they like grease bearings and this would be a sign of failing bearings?
2) If the bearings do need replaced, what is the process for rebuilding these types of hubs?
3) Is this a DIY job or would I be better off having the pros handle it?

I'm pretty mechanically inclined and have rebuilt several grease hubs in the past, I just have no experience with oil hubs and couldn't really find a good answer to these questions. If anyone has a good run down on how to service these things I'd really appreciate it.