I accidentally rippped the lettering off the wiring when taking off the dead thermostate. Anyway, I have only 2 wires coming out of the wall: White and Black. (I do not have an Air conditioner). What colour wire goes to the RH (heat power) and W (Heater control line)?

Will I do damage to my new tstat if I guess?

I have heat for now because I connect the two (black and white) together and it runs continuously.

My furnace is about 40 years old and my new tstat is a "ritetemp 8022C".

It does not make a real difference because you only have a 2 wire sysyem. If it is a new digital thermostat you will probably have to pull a third wire.

Done, I put the white on the R and the black on the W... worked fine... no 3rd wire required