purchased certified used car

Purchased a certified used 2009 Sentra Fe+ from dealership in Nov. 2012 with 17000 on the odometer. Since that time it has been returned for repairs to the hood after it was found to have been damaged in a previous accident that dealership denies knowledge of. Initially agreed to pay for half but after no communication from dealership or body shop during the 2 week odyssey trying to get it scheduled, and then get it back from body shop, I complained and the repair was done at dealership cost. Now, 49000 miles on the car and I am replacing the front suspension one part at a time, initially it was the stabilizer links and now the control arms need to be replaced. The driver side window switch also needs to be replaced. In 1 year, with a car that has not yet traveled 50000 miles the car has had or needs repairs in excess of $1200. I have since purchased my own car fax and indeed the Certified Used car I purchased was in an accident in Oct. 2011 that according to car fax, required the car be towed. When I purchased the car the dealership presented it to me as in Excellent Condition. I have spoken with the dealership numerous times and they deny knowledge of the accident, and further state they do not run Car Fax or any history checks on a Certified used car, even though they provide a Car Fax guarantee. The dealership is willing to invest half the cost of repairs which just happens to be the amount any other garage in Elyria would charge to do the repairs. I do not believe the added cost of purchasing a Nissan Certified vehicle buys you anything. Even with the added cost you should still approach the purchase as if the dealership is going to take advantage of you. I have contacted Nissan USA, they also deny the Car Fax report of previous damage and have since told me it is between me and the dealership, they can offer me no assistance. I have filed a claim against Abraham Nissan with Nissan USA and I further plan on reporting this incident to the BBB as well as explorin