wrenches to take the axel nuts and cones off, take the axel out, clean the hub off well with a rag or shop towel etc... clean the ball bearings off and make sure they arent chipped or damaged, if they are you may want to replace them, if you dont care then be sure to use a ****ton of grease. even if they arent do this anyway. fill the races with grease and put the axel and bearings back in. tighten the hub back up.
Yeah the hardest bit is not dropping the bearings and having to chase the suckers around. Be careful opening it up!
You can't use too much grease, so go crazy, especially the first time. Any excess will get squeezed out of the way when you put it back together and the first few times you ride, just wipe it off with a rag or paper towel when it does and you're sweet. Once you've done it a few times you'll get a better feel for how much grease you actually need and how much is just gonna get squeezed out.