Found out today that the heat exchanger is hopelessly clogged on my hot water "boiler" due to lack of maintenance by the prior owner. We just moved in in April and were unaware of any problems until needed for this heating system. Advise was to replace the old unit (looks to be 20 to 30 years old at least, maybe more) rather than risk taking it apart to clean it due to corrosion, etc. Of course the "home warranty" does not cover any of this (there is an oxymoron if there ever was one). We just put in an A/C system and ductwork. Would going to an oil fired furnace be a less expensive option over time vs. replacing the boiler?