I had to do that on my 1989 3.0 minivan.

First, you will need to get the water pump, PLUS the tubing and "O" rings
from a dealership, because the parts houses do not have the entire pump
assembly, and do not carry the tubing. The timing belt can be bought at a
parts house, though.  You can access the timing belt and water pump through
the passenger side wheel well, but in order to get the timing belt cover
off, you will need to remove the compressor, the pulleys, and the power
steering pump.  Removing the passenger side motor mount would also be much
helpful, so you can manipulate the engine to get the bracket cover off.
Then remove the timing belt covers.  Then go to the top of the engine and
remove the intake plenum (sp) and intake manifold, in the steps outlined in
your Haynes repair manual.  This will give you access to the rest of the
water pump assembly tubing, and "O" rings.  The timing belt is what drives
the water pump, so replace the pump assembly first.  Make sure that you
dress the "O" rings before trying to replace them into the water pump, or
they will slip out of place, and you will waste your time putting things
back together, only to find you have a major coolant leak when you go to
refill the coolant.

Of course, you will have had to make sure all the timing marks are lined
perfectly before replacing the belt.  They are not hard to see, and can be
adjusted easily.

BTW, while I was in there replacing the water pump assembly and timing belt,
I went ahead and replaced the front main seal, behind the harmonic balancer,
even though it was not leaking.  I replaced it because I did not want to
fool with it when it did fail, and I already had instant access to it.  Just
FYI.

I did this job by myself over one weekend, but it is a lot of work.

That is it in a nutshell.  I hope this helps.  I have part numbers and such
if you want them, from the dealership, so you can ask for the right parts
right off the bat.