According to Jim Recap: Cars and Chicks
When Dana needs a new car, she comes to her big sister Cheryl. But Jim doesn't think that chicks can buy cars on their own. He thinks they'll get distracted by the mirrors and lights and everything shiny. As if on cue, Dana almost immediately forgets what she is saying when she notices the new toaster oven on the kitchen counter, and as the two storm out, they forget to take Cheryl's purse with them. But when they come back and say that the car they purchased was several hundred dollars less than the one in the paper, it looks like they got a good deal - until Andy points out that the car is already in the shop, and Dana can't get a loaner. Then they come begging Jim to go down to the dealership and work his magic.
After some begging, he agrees to do so, and he promptly plays the loud customer and gets salesman Bill (John Cervenka) to bring out the manager, which unfortunately is a chick herself. Manager Gretchen (Cindy Crawford) comes out and... Jim heads home with a new convertible sports car.
So Cheryl and Dana head back in a cloud of fury and promptly get nowhere with Gretchen, but they do find out why Jim came home with a new sports car, so Cheryl sends him back to the dealership, and with the help of Andy, who mimics every move of Gretchen (when she bends over, he does too, to offset her powers over Jim), Jim overcomes her hold over him and asks for the owner. Unfortunately, the owner is Mike. As in Mike Ditka, who if anything is even worse than Gretchen.
Strangely enough, however, we do see Mike playing a game with the family back at the house, so presumably everything worked out - but it was never exactly said what happened.
