I am a big advocate of doing things yourself which is why I have recently been telling all of my friends about HVAC forums.
I have told my friends how important I think it is to learn about their HVAC systems before something goes wrong.
I was told when I got my new furnace installed that the best thing you can do to keep your HVAC system running a long time is preventative maintenance. Since I have gotten my furnace installed I have not had to call my HVAC technician at all, and it has been 5 years. I learned online how to switch my furnace air filters and how to do minor repairs. I have had to replace some small HVAC parts but nothing that took more than a few minutes. I have learned so much online about my furnace that I really feel like I am an expert. Sometimes people will ask me about my HVAC system and how I keep it so nice, and I always tell them that I spend a few minutes on HVAC forums every so often. Another great thing about reading HVAC articles online is that you can learn from other people and people will offer to help you. I have probably saved hundreds of dollars by not having to call an HVAC technician everytime something small happens with my furnace. I have even had neighbors ask if I could come check out their furnace! A quick search on the internet for HVAC forum or something like that should pull up a bunch of articles for you, and then you can get more specific and search for things like AC repair!