Cadillac Repair: 1994 Cadillac Deville 4.9 liter, independant shop, cadillac deville

Question
Dealer overfilled oil at last service. 14 quarts mistakenly put in motor along with overfilling tranny.  Car ran horribly.  Drove it about 50 miles on freeway and returned to dealer as it got worse.  They just drained oil to propr level and said it is fine.  Runs rough with a knock. Help!!  What problems can this casue and is my motor ruined.  I want to know what my options are with dealer as they have admitted there mistake.  

Answer
Your main oil seal is most likely blown, which is going to pour oil onto your mounts and send them out the door. Your valve train is probably drenched in sludge, i dont want to seem so dramatic but 14 quarts will destroy an engine. Take it to an independant shop and let them diagnose what is wrong, dont tell them anything about a dealer messing up. Then take their diagnosis back to the dealer.