Some makes have two cartridges available for their mixing valves. There is frequently a version with plastic guts that is sold cheap at the box stores and an all brass version sold at plumbing suppliers and better hardware stores. Unless you enjoy this process go find the brass unit.

Mixing valves installed in multi-family occupancies usually have stops (shut off valves) built into the mixing valve. This permits you to service the valve without shutting the water off. Take off the cover and look for a slot or hex head where the hot and cold lines enter the valve. The fact that there is a valve is usually obvious once you know to look. If they are present you can also head off to procure a new cartridge with the old part in hand.