1990 Nissan Sentra timing chain

Does a 1990 Nissan Sentra have a timing belt or chain? In replacing said, what are factory recommendations?
I have a 1990 Nissan Sentra and I can hear, I believe, the plastic guides of the timing chain rattle after the engine warms up and is running. There is also a oil leak coming from thr crankshaft/timing chain cover seal. If I replace the timing chain(?) And guides and seal what else is recommended for replace while I'm having the work done? Water pump?
The car is in excellent condition and this noise and leak are my only problem. Most everything is original with certain exceptions.