1G 2G stereo differences?

When I got my car (1991 Talon TSI) it didnt have a stereo, so I thought to myself why not get a stock one off e-bay. So I got one from Auction2Go, they sell refurbished factory decks. So when I got the deck I went to my car, but the wire harness would not go in. There are more prongs on the new deck than are on the harness. There is only one place for a plug in the back. I have a 2nd plug that is also back in my dash. Help Please!

Thanks alot. That really helps. What about the plug from the CD Player to the deck? There are 1 too many prongs on the male and of the plug. It is in the middleof the ring of prongs. Can I just pull it out?