I think maybe you are overestimating how much control you have over what you will be doing. Do you have a guaranteed job in your DEP paperwork? If so, that's your job. You'll get some basic education for it in tech school, then when you get to your first base you'll get a lot of OJT. You don't get to say "I'm going to work on engines too," although there are some opportunities to cross train. But that means moving from one job to another, not taking on something else as well as what you are doing. You will likely have lots of chances to do rudimentary work in some other areas, for instance I had classes in BDR (battle damage repair) so that I could patch holes in an aircraft skin using a drill, rivet gun, and a coffee can, but that didn't mean I did sheetmetal work. I was trained in hot pits, so that I could (and often did, especially in war time) take any position in refuling jets "hot", or with engines running, for fast turnaround. I was also a bomb dump augmentee, meaning that I could do basic missle assembly since we were strictly and air-to-air wing. With the exception on hot pits, I never actually did any of those other things, they were strictly war time emergency training so I could fill in if someone got killed. Since I was back shop (in my career field there were back shop guys that worked on the systems, and flightline guys that hung missles) we didn't tend to be doing inspections while we were fighting, so hotpits was where I spent my 12 hours a day in war time. They kept one of us at each pit to safe all the weapons systems before they started fueling, although I was trained and occasionally performed in the other positions as well.

I've dragged this way off topic, and you may not want to hear it, but if you want to hear some of what the recruiter isn't telling you, click my user name and drop me an e-mail. I've been out for a number of years, but I'm still very familiar, with friends still serving, and my wife being a MSgt. with over 18 years in. Be glad to share, and it's not all negative, but it sounds like maybe you aren't getting a very realistic picture of what you are going into.