oil leak

i have an oil leak around the back of transfer box and handbrake drum

is this an easy fix and what bits are likely to be needed

Dont want to strip it til i have the bits

Ideally dont want it off the road at the moment

most of the time you only need the flange seal and not the flange as well but if you want to be sure order both, its not a hard job. unbolt the rear prop, take the drum off and undo the flange nut, remove flange and take the seal out then just clean every thing up and put it all back together.