1991 Mazda Truck Timing belt or chain?

Not a big car guy here. I got a 91 mazda b2600i pickup from a buddy and was wondering how i could tell whether it has a timing belt or chain and when should i relace either. Should i drive it until i feel there is a problem or what do you think. Also, is it okay to clean the engine compartment with a do-it-yourself car wash power sprayer without damaging any components. thanks for your time, have a great day.
justin