Helpful Bike Shop Guys

I don't know too much about bikes and I always feel a bit nervous when I go into bike shops and need something. I'm afraid the person helping me will ask me a really basic question about my bike (eg. What size is it? What size are your tires?) and I won't know the answer (eg. No idea and 700? Maybe? Or 20 something.... I don't know, which number sounds more right?). Today I went into the shop to get a special trainer tire so that my trainer won't destroy my regular road tire. The guy asked what type of bike I ride (phew, I know that one!) and then grabbed a tire. Next he said, "Would you like me to put it on for you?" I tried to sound nonchalant, like puttinghttp://www.blogger.com/img/blank.gif on a new tire is NBD for me, so I said "Oh, sure, that'd be great! You know, while I'm here, and my bike is also here..." I think he saw right through it but it was really nice anyway. So thanks, Guy at Wheelworks!