It probably would be best to completly rebuild the turbo. The bushings & thrust plates being warn is probably what is causing the seal to start leaking. Depending on the type turbo there are some companies that well sell you a kit but not all vendors do this. IMHO if the turbo is a good one and worth keeping it would be better to send it to one of the vendors that do rebuilds incase there was a need for more than just a kit. they would be more app to catch any possible problems and could take care of them and even balance if nessesary. This could also give you the chance to upgrade to diff wheel on the compressor if a little more power was wanted & usauly doesnt cost that much more if its a easy upgrade.
If you do wish to rebuild it yourself I am not sure which of the forum vendors sells such kits (if any). If none of the forum vendors offer such pieces and you need I can supply a few links that may be able to help you. But IMHO you would be better off to send it someone that could asure you wasnt wasting your money on a kit for a turbo that needs more.
If you find you need the links just PM me and I will get them for you.
Jess