I would say the more info they ask for the better, they're showing that they want to fit a bike to YOU, not just sell you something expensive.

But hey - weight isn't personal! Just wait until they ask you if you're getting saddle sores, or if you're wearing underwear under your shorts... Just kidding. But be prepared that they may suggest appropriate underwear, or lack thereof.

If you're feeling a tad nervous about the "athletic guys" try scheduling your test ride to some time they don't have lots of customers, and try to avoid the hippest, youngest dudes with the caps on backwards. Pick some nice fatherly type with a belly to help you, he's probably the most experienced biker there anyway... And if you let your excitement over getting a new bike show they'll all love you