1) they are all plastic with some sort of chrome coating.
2) they are glued on with some sort of double-sided tape. you can use double-sided tape, silicone (clear is recommended), or super glue.
3) you might find them on eBay, or you can go to
http://www.buy-oem-parts.com
4) the size of the emblems might be the same (they are, I checked a long time ago when I took mine off), but the rear one has a curve to it to fit the trunk. the front one is flat.