I think your van will have the 1.8 Endura engine - as the 1.6 ceased production in 1989.
If so, I'm afraid its not a particularly simple job as the water pump is driven by the outer timing belt - the one that turns the cam shaft. The inner one drives the injection pump. You'll really need a manual for this, either a Haynes type, or you can download info from Autodata on line for a small fee. You don't need any special tools for this, but the alternator / PAS belts have to come off, together with the crankshaft pulley.
Cheers John