Gearbox main seal leak

SOURCE: oil leak on main seal

Well those are hard to do it by yourself so I suggest you go to your auto repair shop and have them do it. Of course you can go to different shops so you can see the difference in pricing if any.

SOURCE: 1997 Prado v6 3.4ltr rear main seal oil leak. Can

Motor out is not needed.
You need to disconnect the drive shafts, put a jack under the back of the motor, and put a trolley jack under the box before you undo it.
You do not say if it is auto or manual, removing the box is slightly different depending on which one you have.

Face the trolley jack so it can roll backwards easily, remove anything that may be stopping the box coming down and back. eg: exhausts, gear linkages/stick ( from in the cab if manual)
reverse and neutral light wires, oil cooler pipes.

You will need to lower the box with a couple of easily accessible bolts still in place at the bell housing. Do this slowly with someone watching the engine fan to radiator gap etc, and make sure you do not do more damage getting it out.
Now set both jacks to take equal weight, making sure the box is balanced and secured to the trolley jack before you undo the last bolts.
It is all about balance, alignment and going very slowly with the separation.
Do not rush it. Be very slow and calm. Sudden movements can bend the gearbox shaft, damage your torque converter, or worse, trap you.
When everything is right and secure, you will be able to shake the box by hand and pull it back.
You may have to adjust the height of either or both jacks to take it out cleanly, being very careful of how much you allow the back of the motor to drop and what it may contact or stretch and break as you do so.
Take care and work safe. :)

SOURCE: How to change the manual gearbox oil on Toyota

drain plug on the bottom of the gearbox,fill plug on the side of the gearbox and you only fill it till it just starts to run out and put plug back in should be 24 mm plug

SOURCE: oil leaking from back of motor . changed oil

The oil pressure switch is located on top at the
transmission end of the engine.
If the switch is leaking, it could appear to be coming
from the places you mentioned. Hope this helps.
Good luck

SOURCE: oil leaking from rear of gear box where rear

yup