Product review (5 stars): Pretty much direct replacement
Worked perfectly.  I have an older HVAC system and the fan was stuck on, it wouldn't shut off even when the wall control was turned off.  This fixed the problem immediately and hasn't given me a single issue since.  Pretty much direct replacement, comes with instructions.  It's not like changing the batteries in a smoke detector but if you've determined this is your problem, you can probably fix it, the wires are all on terminal plugs so it's pretty simple.