I worked at a Dick's in college. If you have a basic knowledge of technical running shoes and a bit of experience, you will get the job. I had worked at a running specialty store in high school (no specialty store near my college), so I already had a good start on gait analysis, foot types, shoe technologies, etc.
And while that knowledge helps you in the interview, once you get the job, it doesn't matter. Maybe one out of twenty people who comes into Dick's is looking for advice on shoes; most just pick the "best looking" shoe off the wall and ask for their size. The only time having a knowledge of running shoes helped me was when I was "secret shopped." The typical Dick's customer is looking for the best price on shoes and doesn't care that the Asics GT-2130 is the best for moderate overpronators.
I would strongly urge you to find another job. Between sales quotas (usually on socks, shoe cleaner, or other crap), screwy hours, incompetant staff (you will be shocked who is promoted to manager), the whole Dick's experience sucks (pun not intended). The only decent perks were okay discounts (I think 30% if I remember correctly), lazy coworkers (you look good in comparison and can easily earn a raise), and green shirts. But that's just cause I look good in green.
You may love shoes, but you will hate Dick's.