I am so sorry! I know how frustrating that can be!

My Advice:

-Tell the salesmen to get their asses on the sales floor and quit annoying you. With the economy as bad as it is, they should be focused on selling cars, not nitpicking you for little shit. When you have a free minute or so, you will get them their floor mats or whatever the hell they need. ( I absolutely hated this. Sometimes, my salesmen just had to wait. I had a ton of stuff to do, and didn't have time to run around grabbing accessories that they just wanted to "show" their customers. They just need to be patient.)

-Don't worry about your overnight order not showing up. You aren't FedEx or the parts warehouse, and there is nothing that you can do about it. If the customers are upset, all you can do is apologize, tell them that the order was placed and it simply did not show up. (Then pray heavily for an afternoon shipment! )

-What operating system do you guys use?