Clean the area!
There is just a o-ring that seals the drive motor to the transaxle. The drive motor has a oil seal on the shaft and I think that would be the only thing that could be causing the problem. In the manual, you remove the drive motor, disassemble, remove shaft, remove snap ring, replace seal. Depending on how much room you have, I'm wondering if a person could get the motor out, remove the snap ring, and carefully get the seal pulled/replaced without taking the motor apart. Sometimes a person can use a seal puller to do this. To me, it looks like the hard part is getting the hoses removed and getting the motor out on to a bench.
If the motor is taken apart, there are adjustments that must be done carefully per manual. It must be CLEAN and done right.