new to this house, didn't see the shut off switch when i shut down boiler two months ago. now i have found what looks like shut off switch, have I done any damage to the unit?
If you just shut off the gas without shutting off the electrical, it shouldn't damage the system. Basically the thermostat(s) will continue to call for heat, the boiler will try to fire up and fail, then the boiler should give up and enter lockout. The boiler has safeguards built in to handle a lack of gas, which should prevent damage to the system.