you won't need a new piston because you pull it, but it would be a good idea to hone the cylinder and put on new rings, and then you will have to do all of them the same way. This is a MUCH more finicky procedure and if done slightly incorrectly will cause issues later on. Plus it will cost alot more, take alot more time and introduce the possibility of frigging something up.
As it sits, just take a good, clear, well lit, in focus, non camera phone picture of it and post it up.
MOST likely the piston is fine. At worst, barring really odd conditions, you will have to remove a "divot" out of it, from the valve or you will get hot spots and ping/knock. Some sand paper or a dremel tool and you can carefully clean it up just fine. I have removed 2-4 large divots off each piston on a modified turbo car and had no problems at all from that. Car ran great and ran fairly high boost too, for quite a while. Then he hit a ditch and rolled it, but thats beside the point.
Send the head to a good machine shop and have them pressure check it, clean it up really well and mill it flat. Have them take a bit off, as you are running an N/T engine and the compression bump will help power and mileage. Also have them put in new valve stem seals and replace the valve(s) that need to be. This won't cost as much as a new engine, and it will be MUCH MUCH easier and quicker.
Use a stock head gasket, no need for something fancy, plus your block is not being decked so it needs a head gasket that will fill in minor imperfections, were a metal one won't seal correctly.
Clean up the top of the block really well using razor blades. The single edged ones you get at a body shop supply place.
Don't forget to change the oil before you start the car, it will have coolant in it and all sorts of crap too. DO NOT START IT until you get fresh oil and filter in it and fill the cooling system.
