To answer your questions:

1. Any item from the dealer is going to be costly. You should check around first. Stay away from cheap shops, as the saying goes, you get what you pay. The only thing about the one from the dealer has the MB logo stamp on it so it matches your original one. If you want to keep the car everything original, dealer is the only way to go.

2. I believe you have to change the sliding door. As I recall, the older model that comes with the cassette holder also has the cig lighter in the front. The sliding door on those model is two pieces as opposed to the one piece sliding door for the storage/drink holder configuration. Check out Performanceproduct.com, they even have the wood sliding door.

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95 R129
04 Infiniti G35.5 BS
10 X204