Air Force Mechanical Aptitude area?

I am in the Air Force DEP and i am hoping to get a job as an Air Craft Structural Maintenance, my recruiter called me today and said i booked a job as Mechanical Aptitude area. Is this good or bad not knowing what job you will have before entering basic training? a lot of people say they give you the jobs nobody wanted or they just couldn't find anybody to do. My recruiter also told me i have to take this job because it was on my job listing, is that true?