I think you’re asking about two issues. (1) How to set the clock on a model year 2000 car, and (2) the clock doesn’t display. If those aren’t the two issues, ignore this post.
If the clock doesn’t display, you’ll need to fix that before worrying about setting the time. Dropped pixels are a well known issue. This is a link where the fix for that problem is discussed:
http://www.mbworld.org/forums/clk-class-w208/241804-diy-lcd-repair-odometer-clock-temp-etc.html
If that doesn’t work, BBA can rebuild them
http://www.bba-reman.com/uk/index.aspx
or the dealer can sell you a new one.
This is how you set a clock:
http://www.mbworld.org/forums/1575485-post33.html