Depends on the qualifications and integrity of the manager. If it's someone you know to be well-informed on revolvers, and have a working relationship with such that they're looking out for your best interests, then yes I'd trust their word.

Short of that, though, I think you're best off keeping your own counsel.

At minimum, be friendly but tell the manager you're going to inspect the piece before you sign-off and pay for it. First check the revolver and confirm that all chambers are empty. Bring at least a flashlight and perhaps a magnifying glass or reading glasses, and visually inspect it from every angle. It should be factory fresh and free of any blemishes or handling marks. It will have been test-fired at the factory and sometimes there's a little powder residue; this is normal.

With new S&W revolvers, and especially J-frames, the primary thing to look for is any cracks where the barrel is mated to the frame, especially on the underside; on the off chance there is a problem from the factory, this is the likeliest one. Second likeliest would be a canted barrel, meaning the barrel isn't perfectly aligned with the frame. If you look at the top of the revolver from directly overhead, you can see if the barrel's in true or not.

Run a search here and you will find pictures of these problems. Either would be reason to let the manager know S&W sent a bad one and it needs to go back. Do not pay or take possession.

Otherwise, again making sure the revolver is unloaded and pointed in a safe direction, dry fire it through at least one full cycle and preferably a few to assess if it's functioning properly.

Following are two links -- one brief, one more involved -- on pre-purchase revolver checks. They're intended for used revolver buying, but are informative in general.

Revolver Checkout Procedure

https://docs.google.com/file/d/0B6Fh...hl=en_US&pli=1

Finally, make sure you're getting the factory box, paperwork (owner's manual, warranty card, etc.), bicycle lock, and empty shell in an envelope (proof of factory test-fire).

If all that checks out, you're good to go.