I’m hoping somebody reading this has removed their wiper motor. I need to get mine off tomorrow, reading the Haynes manual it looks quite straightforward, the bit I’m a bit unsure of describes removing the three little bolts at the top of the box then 'UNDO THE TWO CLIPS AT THE BOTTOM. How do those clips unfasten ? The photograph is very grainy and hard to make out, are they sliding clips ? Spring loaded clips ? Does anything have to be undone on the clips to unfasten them ?
To answer my previous post in case anyone else needs to remove the wiper motor and housing. I did it today. It is not a job I’d relish doing again soon. The clips at the bottom of the plastic housing slide sideways, the slotted screws you can see remain attached to the bulkhead. Looking from the front the L/H one slides to the left and the R/H one to the right. Much easier to write than actually do ! The R/H one is completely hidden, ideally you need tiny little hands with universal joints on your wrists and fingers 
They were both siezed solid, hardly surprising after 30 years undisturbed. I used copious amounts of penetrating oil and started with the ‘easy’ R/H visible one by tapping it back and forth using an offcut of round bar as a drift until eventually it released. For the hidden L/H side I cut a slot into the edge of a piece of 1/2" wide flat bar and bent the other end into a right angle. Using only my sense of touch I was able to thread the flat bar underneath the plastic housing box and engage the slot over the edge of the clip and then used the right angled end to hit against, eventually it came free. Even with all the fastenings removed getting it off the car was a nightmare, there is so little room between it and the engine to wrangle it out of the hole and off the car. I’ve cleaned all the rust off the clips so they now slide nice and free so hopefully refitting it all tomorrow will be a lot easier.
