Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
The range should be good enough unless you are towing a hugely heavy load. However, depending on your crank, you may not be even able to change the chainrings since many lower line MTB cranks have the rings riveted, not bolted, on. Even if the rings can be replaced, it might be less expensive to buy a complete replacement crank and newer MTB cranks come with a 22T granny ring.
You probably have a cassette, not a freewheel since freehubs were common by the '90's. And yes, if you change the cassette or freewheel, use a new chain.