Thanks for the comments.
To answer some of the questions:
Our tankless heater is a Girard. It is propane fired since our MH is a gasser.
When I mentioned that our dealer won't talk with us about replacing it we have been trying to get him to give us an estimate on replacement of a conventional water heater. Instead he has contacted other past buyers in our area and they have phoned us trying to resolve our problems. We are not asking them to make the change for free, we are asking what it would cost US to replace it.
Shirley