You're 99 CLK does not carry a maintenance free contract as does the new models. A & B services come out of your pocket. My opinion is to definitely bring your car in for the service. It's not just an oil change, there is a list of things that are checked (tire wear, brakes,fluids, etc.) This would be your first A service and expect your B service roughly 10k miles down the road (depends on oil quality/elapsed time). I also think that changing the oil in between intervals is a must. There's no way that 8-10k miles on the same oil will keep your engine clean and healthy. I've seen oil filters crumble in your hand from this. On time services are a plus with your vehicle history. My 2/100.