Auto Matrix

We bought a Chevy Blazer from them and had it 12 days and it died on my husband on the side of the road in a snow storm. After it sat there for 3 days Auto Matrix finally towed it to their shop. Now they are saying it needs a new motor that will be at least $500. They are willing to provide the labor at no cost to replace it but we will have to pay for the motor and they will not take payments on the motor. $500 down to have a car for 12 days....doesn't sound like a good business practice to me.