On an oil system, a technician will usually look at the fuel supply, filter, nozzle, and ignition before going further, and on gas equipment at the igniter, flame sensor, and venting. Electric heat calls tend to start at the panel and thermostat. Clear the path to the basement and to the boiler or furnace so the work can begin as soon as they arrive.
A simple repair may not need paperwork, but replacing equipment in Whitman goes through the Building Department at Town Hall, which issues gas, electrical, and plumbing permits. Inspections are scheduled by calling the inspector directly, and the gas and wiring inspectors list early-morning call windows, so ask the contractor to handle that.
If the technician finds a cracked heat exchanger or a failing chimney, they may shut the system down for safety. Ask for that finding in writing so you can get a second opinion before agreeing to a replacement.