I have a ten year old (propane) gravity wall furnace that came with it's own wall mounted thermostat, which is a Honeywell "Millivolt". I am now relocating the thermostat, because of a small remodeling, and want to replace the thermostat with a more up to date (looking) thermostat. Can I just go to a home improvement store and get a "universal" replacement thermostat? What do I need to know? Thanks,