The part is cheap relative to the job, so it is worth replacing related seals and the expansion device at the same time.
Evaporator leaks are usually found by dye or by electronic leak detection, because the refrigerant escapes into the cabin and leaves no trace in the engine bay. A musty smell with poor cooling often means the evaporator core is fouled with debris rather than leaking.
Listings state whether the evaporator includes the expansion valve or orifice tube and whether new O-rings are supplied. Reusing old O-rings on a new evaporator is the most common cause of a leak after the job.
Because the dashboard has to come out, many technicians replace the heater core and the blend door actuators at the same time.
