I don't have any PC's, though there is a PC for Paradise Estate going on right now that looks like $175 is fair for a Pick-up. Shipping is a beast on it, so local pick-up is beautiful.
As for HOW to ship, it's not heavy, but it is big and a little fragile. With some care, I know the roof and walls will come apart, which will make the box a lot smaller. Be sure that the buyer knows that you are taking it apart, of course. If it were me, I would try a local-meet up or something like that. For a beautiful playset, I would be willing to drive from Minnesota to Missouri, but that's just me.
If the buildings won't come apart, just a sturdy box, maybe even a box in a box, and lots of packing material. I would use crumpled paper (don't let the newspaper touch the building, just in case the ink rubs off) or bubble wrap because packing peanuts could allow the building to shift, and if the carrier drops the box, the old plastic could crack.
You could use fakies or McPonies for packing material! That would be heavy, but really funny!
Good luck- hopefully you'll get some PC's quickly!