Actually, when you open the door , the dash gears up showing the milage an so forth. The block as you say, stays that way until you start the car. That's when you see the "P". Was the car doing this when you bought it? Yes, then other owner can tell you what happened an when. That will give you clues ,maybe, as to which direction to proceed. What codes are coming up? The dealer's should have given you a sheet ,telling what they did and what they found. That would help us get some direction. Don't junk it, offer it to someone here. Have you tried to put it in gear using the emergency release?

Edit : So the cars not even starting...forget the shifter !! It has to run to see a P in that box!!! What are the set codes... This is very important to us to help you.!!