The contactor, as the partner says is in the gearbox the first, the exact position is usually in the front or superior of the change. A two -cable connector comes to that contactor, that if the bridges with the contact on the back lights.
The contactor is threaded in the box and to disassemble it, it is enough to disconnect the cables and loosen it. Note, the valvulina of the change may come out, depending on where the sensor located in the box is, you may have to replenish some valvulina, but it is nothing serious or difficult.
All the best.