On a gas furnace, the technician will usually read the error code, check the flame sensor and igniter, and confirm the pressure switch and vent pipes are working. On a hot water boiler they'll look at the circulator, the controls, and the system pressure.
If equipment has to be replaced, Randolph takes building, gas, and plumbing permit requests online through PermitEyes, and the gas fitter on the job files the gas permit. Ask the contractor to confirm the permit before the new unit goes in.
If you're selling soon, note that the Randolph Fire Department's smoke and carbon monoxide certificate for a sale is valid for 60 days, so heating work and alarm changes should be coordinated with that inspection.