Yes. If you get a Lexus, get an SC. I think I know who can explain everything about the Geico extended warranty in detail: GEICO. Call them. They may impose certain mileage and or age maximums on the program, so you will need to know if you will still be able to get an e36 under it (7 year, 100,000 mi is nominal for bank financing). To be honest, I seriously doubt this will be as good as you are hoping.
Call them up. Fifteen minutes could save you from getting your parents to pay for a car you don't like.
[The advice above is for your pursuit of a BMW. Personally, I would quit pushing it and be searching for something my parents would approve]