Work the safety and the decocker, check the feed ramp, pop in and out both magazines, rack the slide a few times to be sure there isn't anything obvious that is wrong.
I would pay specific attention to the decocker - if you rack the slide once (unloaded of course) and pull the trigger, you should feel the smooth, lighter SA trigger pull. After you decock it, you should have a stiffer trigger pull.
After seeing a recent thread here, I wouldn't trust the decocker until you've used it at the range a number of times and it works correctly. I'd keep the barrel pointed in a safe direction, like downrange, when using the decocker.
If you're of a mind to, just break it down right there at the counter. You could give the whole thing an inspection before plunking down your hard earned money !