Dada5 Congrats on your new car. While 320k miles is a lot, the wires on these cars are usually replaced in singles as needed. Check the resistance of each wire- if one is in spec, keep using it, if out of spec, replace only that one wire(this is not chevy). If you replace all 16 wires, it will be quite pricey. I would strongly suggest and seriously consider buying the correct tool for removing each wire, it will make the job much easier. The wires usually cannot be removed by hand from any of the coils. It is available on line from Benz specialty parts houses. Otherwise you may damage the wires. If the sparkplugs look worn, then replace all 16 w/ correct replacements. This car may have a tool kit in the trunk with a vehicle specific plug tool. If plugs look OK, I would just drive the car and monitor the front sparkplugs on occasion. As others have mentioned, you MUST use anti-seize in the plug threads, no exception. You are wise to change the oil and air filters. The key to the twin filter air box is to line up everything precisely and it fits right in. Be sure to replace the oil drain-plug crush washer every time or it will leak(I have gained a number of Benz customers due to some shops not doing this). 5W-40 synthetic oil is what is usually recommended for your car. One more note, while this car specifies 8.5 QTS oil capacity, I have had many a late model Benz similar to yours show full adding 7.5 QTS or up to 9 QTS of oil- just do not overfill. The transmission uses a low viscosity synthetic fluid. I recommend to my customers the OEM MB synthetic fluid or the Amsoil Signature Series low viscosity ATF (assuming yours is an automatic). Just do a drain and fill & filter with such a high mileage transmission. If these cars are given strict excellent maintenance, they tend to last a long time. Good luck with this car and may it go another 320k.