I'd suggest leaving them attached to the scrapbook paper. I have a couple of skinned OJs and I wish they had something attached to the back. you can cut them out just leave extra paper around the borders, don't cut too close to the card. I also don't think grading will add much value; however, they are valuable.
Here is one Leon and Scott had in their auction:
http://www.b-lauctions.com/site/bid/...etauctionid=80