The S&W produced PPK & PPK/s retails for $556.00, but that is only the suggested list price. Most shops sell them for much cheaper. I have a PPK/s made by S&W and purchased it for around $475. One thing to keep in mind, however, is that the price of a particular firearm will vary drastically with the area of the country you are in. As for the contents of you box, that is the standard kit that comes with the PPK.
Many smaller shops keep a limited supply of certain models and yours may have been one of them, for that particular establishment. So I would not worry to much about getting the display model. I do not understand though why they would not order you the finish (color) that you preferred, unless it was no longer produced. All PPK and PPK/s are available in stainless and the only blued model available is the .380ACP PPK and a two-toned .380ACP PPK/s.
If you are looking for only the finger extension for your flat based magazine, I would call Walther America (aka S&W) and inquired to their availability. And while they are on the phone you can also purchase your spare magazine. The magazines for the PPK is fairly easy to aquire, try sticking with factory Walther or Meggar magazines though.
As for the "restrictions," that sounds like a load of ballocks. The maximum capacity of a factory magazine for the PPK is 7 (.32) and 6 (.380). Even in states that have limited capacity restrictions, the max by law is usually 10. Oh and for future reference, there are 10rd PPK & PPK/s magazines out there, but they are fairly difficult to come by and are not produced by Walther.
Hope that helps.