I've replaced a front windshield before and although I cannot tell you the complete process I know that you must kick the old windshield out from the inside.
By calling a company that installs auto glass. Not a DIY job.
It is located behind the rear seats. Once you remove them you will see the pumps and lines. There are several youtube vids on how to remove and replace it.
Raise the wiper blade and hold. Pull the release on the bottom of the blade and wiggle it off.
They are in the rear of the engine. Two can be reached byt two more are between the bell housing and the engine. Not a do-it-yourself job.
Center of the rear head.
at roof
The washer fluid for the rear liftgate is supplied by the same reservoir as the windshield in a 2000 Mercury Villager
It is on the top rear of the bell housing.
I'm pretty sure that it is integrated into the either the front or rear windows. Therefore you would have to replace the windshield, or rear window.
It is behind the rear seat back.It is behind the rear seat back.
The washer fluid for the liftgate is supplied by the reservoir for the windshield according to the 2000 Ford Explorer Owner Guide
any windshield and glass replacement shop will do that for you