I have a question. Why is the center armrest plastic and not leather? Are there leather replacements out there??

yes, there are replacements. My 2001 CLK55 center armrest is plastic as well. I replaced mine with a leather/wood one which I ordered from formymercedes.com.

You can find some neat, inexpensive mods on this site, including the AMG lit doorsills.

I'd love to find a real leather replacement. It's weird that it's not leather in my opinion.