Which car should I get? And what are the advantages of having certified used?

I have to share a car with my twin and we turn 16 on Sept. 3. She insists on getting a used shelby mustang. One, insurance will be ridiculous. Two, they do not come in automatic (we can't drive a stick shift, and neither can our parents). Three, it is way over our 30k budget, even used. I could go on. And YET, my parents still continue to side with her. Whereas I want a Certified Infiniti FX or G37. They come in AWD, and are automatic. Therefore we can drive in summer and winter, but we couldn't drive in any season with the mustang because we don't know how. And the Infinitis I have found are certified, therefore they have been inspected. Does this mean they also have a warranty because in their descriptions they say, the warranty will be extended to August 31, 2014 or 100 K. This is an extension on of the original Infiniti warranty and has $0 deductible and covers even navigation and audio systems if the vehicle you choose is equipped with navigation. Also by certifying this G35X you are eligible for special interest rates offered by Infiniti Financial Services. With approved credit you will be eligible to finance it for 24-60 months at 1.99%. If you are not interested in certification, deduct $2,095 from the sale price. Does this mean the car still has a warranty or just the powertrain? My mom swears up and down it's just on the powertrain, while it may be I don't know, and continues to use that in her case for the Mustang. The Mustang she wants is roughly 45k, and has navi and everything. I have found several infiniti's with the same ammenities for only 25k-30k. Which would be more reliable and will it cost more to fix an infiniti if it breaks down? The nearest Infiniti dealer is 86 miles away, so would I have to have it towed there to be fixed?