The most common fault with these units is that the joystick stops working; certain directions stop working and you find yourself having to push down on it to make anything happen
First thing is getting it out. Use a screwdriver with a bit of electrical tape wrapped round the end to avoid gouging the plastic or door handle on the side and pop it out. The drivers side switch has 2 connections going into it, one of which has a strange clip you have to sort of rotate to get out. Dont just try and pull it, the clip lifts itself out
You will see the unit is made of 3 sections. using a small screwdriver again, gently lift the flaps to release the 4 catches holding it together.
Hold it with the joystick at the bottom as you open it, there are small bits of plastic that like to fly out
justinaccurate has attached the following image: