It's not really hard but there are a few things that need special attention. I believe they are explained in the FAQ section, thats the link in the right text box of this sites homepage. I know it says 700/900 but your motor and water pump are the same as the 900 series cars.
I wouldnt touch a thing until you've got all the parts at hand, Hepu pumps available at FCP groton seem to be the recommended replacement if you dont want to spend the $$$ on a dealer part. For a few extra dollars you might want to add an extra gasket set to your order, it may come in handy.
The pump is held in place by 4 (IIRC) bolts and 2 studs. You slide it on over the 2 studs through 2 elongated holes in the pump and then lever/muscle it up into place where a rubber o-ring seals to the head. Once its in the correct position you can get a couple of the bolts started, I used some silicone sealer on the o-ring for a little insurance.
The connection of the metal tube that connects to the back of the pumps output can be tricky. I think the best way to do it is to find the bolt back toward the center of the block below the exhaust manifold that hols the tube in place and remove it so the tube can be moved around and fit into its seal after the pump is secured in place. A bit of silicone on the o-ring there can make things easier as well.
Once everything is back together and sealed up wait overnight to let the silicone cure, put in your coolant, pre mix or correct amount of coolant(@1/2 the system capacity) and top off with water(distilled is best) Then fire it up and wait for it to get to operating temp and check for leaks. If there are any leaks you will have joined the exclusive club of most of us who have changed a redblock water pump for the first time. Then you grab that extra gasket set that you figured would be a waste of $$$ and try again.

Seriously though I think if I had done my homework a little better ahead of time and known about the "special attention" items I probably could have had a leak free install on the first try. With that being said, the next time I do it I'll still get an extra gasket set.

BTW: this is a good time to swap in new hoses and belts if needed.