How to take care of my first luxury car?

I STRONGLY recommend that you introduce yourself at the nearest Mercedes-Benz dealership. They will be happy to provide you with a maintenance schedule if you can't be bothered to read your manual or have lost it. Generally speaking, with modern Mercedes cars, they need an oil change annually (~$125), and REQUIRE full-synthetic oil and a special synthetic-media filter available only at the dealer, or a specialist shop. You need to have the brake fluid replaced every 2 or 3 years (~$100), and the transmission fluid replaced every 40k or 4 years (~$250) - the usual stuff. Periodically, the car's computer will remind you that it needs other services depending on ambient conditions and how you drive.

A dealership can also provide you with suggestions on modifying the audio system, perhaps with a Bluetooth adapter or simple cable. As for the cosmetic issues, it depends - "detailed" is a VERY vague term. You don't give us enough information. If you keep it clean in the first place, you may only need the inside cleaned once or twice a year. If you're a slob, maybe every month or so? As for the exterior, you haven't told us if you live in a dusty or wet area, if the vehicle will be garaged, if you location uses road salt in the winter, etc. However, I get my Mercedes E-Class washed at a professional touchless wash every other week, and detail it once in the spring after the winter weather is done.

Last, ALL 2006-2008 Mercedes-Benzes with the engine your car has (3.5 L M272/3) have a major, known problem with engine failure caused by defective balance shaft gears. There are two class-action lawsuits ongoing about this. If your "Check Engine" warning light ever comes on, take it IMMEDIATELY to the dealer. It's usually less than $4,000 to repair, unless additional damage has occurred. You don't state the vehicle's mileage, but the problem usually manifests between 60k and 90k miles.

Nice, a relative "randomly" gave you a Mercedes and you're worried about how to make it play music. We should have a Yahoo lottery to "randomly" guess your age and how long the car will last.

Keep it clean , don't get into a car accident, and maintain it all good :D !