it depends. are you just going to install new bearings with the diff or do you want to replace all the bearings in the trans? if the latter i suggest you go all out and do a full rebuild, replacing the syncros blocker rings while you are in there. this requires a press and the knowledge of how to rebuild a transmission as well as the tools to do so (a press and bearing puller adapter, as well as a slide hammer and bearing race adapter, various snap ring pliers, magnet base dial gauge, and various mounts for the gauge). the parts are also expensive, at about $600 for a kit, but you get all the bearings, races, seals, and blocker rings needed to rebuild the trans. I do recommend rebuilding it while its out (if you arent sure check all of the syncros) and i highly recommend taking it to someone who knows what they are doing.