Mechanical Parking Brake problems of the 2000 Chevrolet Suburban

I bought the vehicle from a private seller and soon found that the parking brake pedal would go to the floor with no resistance and would not hold the vehicle on even the slightest grade with the transmission in neutral. The parking brake shoes were worn down to the metal and one of the parking brake drums was deeply gouged. The shoes and one rotor was replaced, which allowed the vehicle to pass state inspection, but now the pedal goes to the floor again and the parking brake does not hold. It is due to be inspected in September and probably will not pass without another $500. 00 in repairs. I have not driven the vehicle with the parking brake on. I have found through internet research that this is a very common problem with this parking brake system and feel that gm should fix this problem. I have the old rotor but not the shoes.