Hi folks, I have an old mercury Honeywell thermostat with two unmarked wires sticking out of the wall. They almost look like thin audio cables, with one lighter than the other. I was planning on replacing it with a new Thermostat for the forced hot air gas furnace (which is probably about 10-20 years old now). Would it damage either unit if I connect the wrong wires (i.e. switched) to the W and RH connectors on the new thermostat? Sorry if this sounds stupid. I'm obviously a noob.

With your setup, just hook one wire to r and one to w and you will be fine. Doesn't matter which goes where. Hook er up, and you will be in heat. Take care, and please let us know how things work out.

Things worked beautifully! I also did some further research and read that this configuration is just an "interruption" in one line- so it doesn't really matter which is RH and W. Thanks for confirming it for me!
:-)