First of all get the car as high as you can, To get that bolt get a jack to take the weight of the gearbox, undo your 4 14mm gearbox mounts and lower the gear box just far enough that it doesn't pinch the rubber drive shaft seal.. This will give you enough room to either get a ratchet spanner in there OR with the help of a mate come from the back of the gearbox with a heap of extensions and an elbow or two.. You guide the socket onto the bolt while your mate uses a ratchet to undo it from the back of the box... Know what I mean?