Changing the timing belt is a tough job, due to the lack of clearance between the front of the engine and the side of the car.
When you change the belt, change the idler pulley as well, as it's probably on it's way out. You will probably want to get a copy of the BGB for your car (toyota's service manual, here's one for 88-89, which should be fairly similar:
http://dropoff.dreamhosters.com/mai/...PAIRMANUAL.zip ), and here's a page that has some tips on the process if you scroll down:
Drivetrain Repair Info
Just search that page for "timing belt" by hitting ctrl-F in your browser.