Is a mercedes benz s420 a good car for me?

i have been looking around for a mercedes benz, this is the car i have been wanting for a while. i really like german cars because they are built to last, very durable, hugs the road and have seen them go around a spike strip at 120 mph in police chases without skidding out of control (im not ever gonna run from the police). i have heard of diesel mercedes lasting a million miles. i know these cars can go 10,000 miles without an oil change and parts can be expensive but im going to school to go into the automotive field and i can get parts for dirt cheap. is insurance expensive with these, im 18 and gonna be going to college, im also easy on the gas pedal, i coast going down hills and im easy on the brakes too. i can get 20 mpg with my dad's truck and 30 mpg in my mom's caddy. and how is the gas mileage for these.