Fix or replace heater to improve selling a home in NM?

Home in a small town just outside of Albuquerque has a heat pump heater for the home. The home is 18 years old, custom build. The heater in the home stopped working. Repair people have replaced several parts but do not guarantee that the unit is repaired. Replacement of the actual unit is expected to be around $17,000 – $24,000. Is it better to attempt the repair or spring for the full replacement when it comes down to selling the home?