Yes, you should replace it as soon as possible. 100k or so miles is as long as you can safely go without changing the belt.

While your in there, replace the spark plugs, PCV valve, crank/cam seals if they are leaking, idler pulley if its rough, tensioner if its rough, water pump, valve cover gaskets, and probably others I cant think of right now.

88 4R, 350 V8, R150 5 speed Sold <...uot; />
97 4R, stock, daily driver
98 Sienna, kid and dog hauler, wife's ride