On a gas furnace, expect the technician to test the ignition, flame sensor, pressure switch, and venting, and to check the flue for carbon monoxide. Oil furnaces get a look at the nozzle, filter, and electrodes, and at the heat exchanger for soot or cracks. Many repairs end there without any paperwork.
Replacement is different. A new gas furnace means a gas permit from the Building Department, filed on Abington's OpenGov portal and inspected by the town's Plumbing and Gas Inspector. A new oil furnace or burner means a Fire Department permit. Ask the contractor to name the permit on the estimate.
If you're replacing an oil furnace, it's a sensible time to compare a new oil unit with natural gas, if a National Grid main reaches your street, or with a heat pump. The contractor can explain what each would involve in your house.