You can definitely say you want to check it out first. If they press you for a good reason, just say "because if I'm going to spend this much money, I want to be sure it's what I want"
Also, check to make sure the touch screen is good. I almost bought a second 3DS last month that was firmware 7.x but ultimately backed out because the touch screen was bad and refused to re-calibrate.
EDIT: Oh, and btw, I just checked craigslist where I live. There are four 3DS listings for $60, and at least two of them, in the photos, are DEFINITELY pre-9.0 (no theme button). No chargers, but you can buy a charger for $2 on Ebay. I did, and my charger works great. So yeah, check craigslist for older models. You'd be surprised how many people don't update their systems.