This '93FSM will walk you through the process step-by-step w/plenty of pictures. The procedure is in the Engine section.

For a shop or dealership you are likely looking at around $400 for 2-3hrs labor and the cost of a new belt.

According to the dealership, Toyota no longer recommends changing he water pump every 80k along with the t-belt, they now only recommend replacing it when it starts to weep, leak, make noise, etc.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed