I had a service call the other day and I was amazed at how much people just dont understand that your furnace is more that a mechanical heater so you stay nice and warm in the winter. They also dont understand anything about Carbon Monoxide or how dangerous you furnace really is. First and to piont yes the unit belongs to the home owner if they wish to fix them themself, just understand that you might make it harder for a good service mechanic to fix it later costing you more in the long run.

 I have been in this industry since I was 14 years of age. I can honestly say home owners cause themselfs more problems. They watch youtube video's and all of a sudden they think they are a service tech. When it comes to furnace repair their is a couple of things one is carbon monoxide and the other is Gas. Carbon monoxide every single year people die from it. In Saskatchewan Canada there is a least one death evey single year. Gas explosions happen all the time. 

I have home owners call me up to buy gas valves and ventor motors  and many more parts that are serious part replacements. A perfect example of this was just yesterday. I went to the supply store and I watched a lady go in after I came out. They sent here out to my truck she ran and started showing me pictures of what she needed. No service mechanic would have done what they did I told her she needed a service call and she said she just needed the part I explained to her that no supplier was going to sell the part to her I also explained to her how much it would cost to fix her furnace. She did not care The part that was need was the inducer motor that puts the bad carbon Monoxide out of the house. I also explained that to her as well. I also explained that if it is not done right what can happen. 

Some people need to realize gas fitters are train to work with this stuff. There is a reason we go to school. I personally have the highest license you can get and I learned from John Dutton was my professor in college. John dutton was the expert that produced the book on the fundumentals of Natural Gas. All gas fitters around  the world probably have read his book. In canada you would never pass the gas fitter exam without it. You would not even understand anything about gas without this man knowledge. 

I was his top student and I have taught myself, But I rather be in the field working just me. I am 51 now with more than 36 years in this trade I have been self employed since the age of 21. 

The best thing i can say and advice to home owners read and find out what you are dealing with before you make a serious mistake. contact a reputable company with good reviews and let them fix it.