You have to know the basic information you are going to fly for them...
A lot of the info can be found in the internet, smartcockpit, manuals, etc.
examplle: Sweepback angle of the 737 wing?: 25º... why? because of aerodynamic reasons i would anwser..
I don't think they expect you to know the 737 100% (unless you are type rated) but the basic info yes. You have plenty of info about the 737 on the web, and if you book some hours on a sim to practice for the interview the place you go they surely will give you a lot of info you have to know for the interview about the 737.
have fun.