No dealer is going to take this car in on trade without a very significant amount of money down. Here's why:
Even though KBB said this car was worth $8,000, you still have to figure in the fact that the dealer has to replace the engine and the bumper, and anything else that may be damaged, just to resell the car. With a retail value starting at $16,295 (before figuring for mileage - KBB allows 15,000 miles per year, so you're deducting for 35,000 miles), and a retail of roughly $12,495 after mileage, they need to be in the car no more than $8,000 to make a profit. However, they need to put a new engine in the car, as well as a new bumper, which, even at cost, will be close to $8,000 in repairs (to include labor). This cost alone would put them over the retail value of the car, and they would have to sell it for more than that, just to turn a profit. They can't do this, as the bank would only lend up to 125% of the retail value of the car (called loan to value), to include tax, title, and license. 125% of $12,495 is $15,618.75. They would make nothing on the car as it is. Let's not forget the fact that you owe $22,000, which would have to be paid to the lender, just to get the title released so they can sell the car. What does all of this mean? It means NOBODY will take this car in on trade. Wrecked, and with a blown engine, the car has no trade value. Even if they gave you $8,000 for the car, and you bought a $20,000 car (max on the loan would be $25,000), after tax, title, and license, you could only absorb $3,000 of the negative equity. You'd have a $500 payment, but would need a down payment of $11,000.
In reality, you've dug yourself a pretty big hole here. You have VERY few options, and none of them are good. You can a) save enough to replace the engine and bumper, and pay the car off, b) allow them to repossess the car, and repay what you owe minus what they sell it for, or c) buy a beater, and file bankruptcy. They can repossess the car, and you can keep the beater, and no money comes out of pocket for the Kia. You will, however, have to pay the attorney for the bankruptcy. Keep in mind, though, that if they repo the car, or you file for bankruptcy, your credit is trashed.
I wish I had better advice, but I don't. Sorry I couldn't help more.