The "seals" on this transmission that can leak are (1) either of the two axle seals, these are relatively easy to replace, the suspension must be partially disassembled and the axle removed from the transmission to gain access to the axle seal. (2) The gearbox drain or gear box level check plug both have replaceable aluminum washers under them, (I have seen people over tighten these plugs and crack the transmission case!) (3) There is an oil seal between the gearbox and engine which may be the source of your leak. The gearbox must be separated from the engine to replace this seal which is a more labor intensive job.