Deductions & credits

The sale amount would be the trade in value times the business use percentage, so $787 looks correct. 

I think you are looking at this screen when you are asking about the cost entry. You can leave that entry blank since I assume you didn't trade in list property to acqure the vehicle. TurboTax knows the cost of it so you don't need to enter anything for the cost.

You new car does not take the old car into consideration for it's value. That used to be the case when you could do a like-kind exhange, but that doesn't apply with 2022 tax laws. The cost of the new car is what you paid for it.