My townhouse has a downflow 1994 Rheem 2.5 ton HVAC unit on its roof (combines both A/C and heat). We have had two issues with the unit and have been in the townhouse for a little under two years. In this latest case, the contractor noticed there was a crack in the heat exchanger of the unit, requiring him by law to shut off the gas and electricity to the unit. His recommendation was to replace the unit completely, in that the amount of labor spent on this and future repair work would overshoot the cost of complete replacement.

I am liable to agree with the recommendation of the contractor, but wanted to ask and see if there was anything out of the ordinary I should be aware in considering the HVAC unit's replacement?