Not able to get heating service

I need to get my oil furnace tested before the holidays hit. I am having Thanksgiving at my house this year plus I want my heating system in tip top shape. I want the heating system cleaned, oiled, plus tightened. It would be a disaster if somehow my heating system abruptly shut down while the guests were over. I have tried getting a heating service appointment, but I can’t seem to get an appointment. Apparently all of the HVAC contractors nearby me are booked solid these next few weeks. I keep putting my name on the waiting list in hopes that one will find time to squeeze me in. Even after waiting all week, I have not heard a peep from any of the companies. It is looking like I will have to splurge for emergency service or pay for holiday heating service, which can be expensive. If I do the emergency service, this is paying a Heating, Ventilation, plus A/C corporation almost double their normal wage. If I do the holiday heating service, the price is bumped up because the demand is so high; Honestly, this one might be more high-priced in the end, then so what do I do about my heater? Is it worth spending a ton of currency to get the heating component cleaned? I am now wondering if maybe I can do my whole heating system service. I recognize I can open the heating system up plus clean; Maybe it can go without oil plus tightened parts for a little while, then getting heating service after the holidays will be dirt cheap too. It is taking quite a chance on my heating system though.

heating service