I did a search on the topic but I'm not too sure do I need to disconnect the speedo cable from the cluster? Or does the speedo cable has enough slack to pull out without being disconnected?

Thanks!

The speedo in the W210 is electronic and thus there is no mechanical speedo cable. There will be a few bundles of wires hooked to the back. I don't know for sure on the W210, but I believe there should be enough slack to disconnect them after you slide the cluster out a bit. Maybe someone who has personally pulled a W210 cluster can chime in from experience.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

As Ali says, there is no mechanical speedometer cable.

You need to run the steering wheel all the way down and back (toward the driver's seat) before pulling the unit. If you want to pull the panel to change bulbs, it is not necessary to disconnect the cables as there is enough room to maneuver the unit toward the driver's door and invert it with the cables in place.

If you do unplug any of the cables, DO NOT turn the key from the 0 (off) position until they are properly reconnected.