Just an FYI. .. fitting the new latch is not a 5 min job... it involves taking the glass out and drilling rivets out of the aluminium skin and taking the window frame off and splitting the door into 3 core sections ...
I'd highly recommend changing the triangle black bits that corrode at the same time, as you need to strip the door for this also
If it's the front doors of course they don't have them.
If the motor is working it's usually the micro switch in the catch that fails.
I'd be interested in finding an easyer way of doing it that's for sure .. my rear drivers packed up only 3 weeks ago... I was desperately hoping it was the motor ... no such luck sadly