http://www.bearingbuddy.com/install.html for bearing buddy info
http://thetrailerguys.ca/index.php?main_page=page&id=4 for regular setup.
The BB are super easy for maintenance and BB installation isreally easy. To re-grease (re-pack) existing bearing, at the very least you should replace the bearings as the existing bearing have to be completely removed and hand packed (this involves putting a dob of grease on your hand and pressing it into bearings until completely filled (no voids and grease is pressed out other side), then re-installing the bearings on the spindle. Hardest part with that is replacing the races (outer ring) if they're worn, although you can re-use if they are in good condition (requires and hammer, punch to remove from the hub and a piece of same diameter pipe for re-install to seat properly and easily).
I'm pretty sure you can add a bearing buddy (from what I remember) to the regular set-up without removing the bearings from the spindle as it basically replaces the dust cap, but its a good idea to check for bearing and race for wear and corrosion. Fresh water can still cause corrosion. Main issue is driving long distances and dropping warm or hot hubs in cold water. this causes shrinkage and sucks water into the assembly. If not pushed out water stays trapped. If the bearings are very old the other concern is the inner seal. Inspect and make sure your grease isn't just going straight out he back of the hub.
If you're relativity mechanically inclined (can change the oil in your truck or pads on disc brakes) this might be a two hour job first time, assuming you'll have some difficulty removing and re-installing the races. watch a couple YouTube videos to get a good idea. This is a really handy skill to have if you blow a bearing on the road as this can be done roadside fairly quick if the race has not been compromised (gouged , worn etc.) and even if they have been compromised you can usually get back on the road and to better equipped facilities.
