This may be a dumb question, but if I abandon the radiant heating system,
can I shutoff the water running through the pipes and not have to worry
about some other unanticipated problem later on?
In general I think the answer is yes but I thought that by shutting off the system entirely you can damage the system. Considering you don't want to use it anymore, fine. However, resale value? I don't know. And should probably drain the whole system first, right?
It is my understanding that you can. The previous owner of our home did so and installed baseboard heating in 4 zones, so that you could selectively heat the home, without heating the whole thing, which is how the radiant system worked.
During inspections, the radiant system was tested for leaks and came out fine. The inspector indicated that we could use it if we wanted to. My guess, from the little bit I know about radiant systems (which have some similarity to the baseboard system, since both use steam generated by a boiler) is that to "reactivate" the radiant system, one would have a qualified specialist come out and flush the system, hook it up, and then test it to be sure it was working correctly.
I cannot imagine why installing an alternative heating system would reduce resale value, unless along the way you also ruined the radiant system so that it could no longer be used.