Visit
www.car-part.com to find an engine in your area. Also, EBAY, as already mentioned, is something worth considering. If the engine is low mileage and is sludge free(easy inspection), I wouldn't worry about needing a 1 year warranty.
Also, visit
www.parts.com to see what a new engine costs. You would've been better off with a shortblock+head combo from the dealer.
Any newbie mechanic would've diagnosed a sludge related oil failure as instant replacement or full rebuild, not just simple dealer parts replacement. Oil starvation damages the ENTIRE engine.
I'd love to see a copy of the dealer reciept.
I'd also keep the car, even with noise. You need to pay it off and recoup some of the wasted money. When the engine finally fails(if dealer ever gets in running reasonably well), then swap it out.
And, never go back to the dealer.
