As one with mechanical apptitude, the less you know (about the position) the better. You must be a good listener and be able to make folks feel at ease. Customers will respect your service to our country. Consider "USAF Retired" on your business cards should you hire on. I have 4 years in the industry now as a "Comfort Consultant",
"Sales-Engineer", whatever the title, it has been very rewarding and I have risen to the top of the ranks, working for the oldest outfit in town in the biggest HVAC market in the desert southwest. I really get the feeling you will do great as well.
What to expect? It's hard to say how a first interview will go but I think you'll fly through it. ( ha! Get it?) Good luck and let's hear how it goes. I can honestly say that I really love what I do and it pays really well also. (Just an added bonus)
Cheers,
Charlie