Will this plug directly into my existing harness?

Yes. The factory connector matches OEM Mercedes electrical specs — no adapter or rewiring needed. Push the new switch into place and you're done.

Does this control all four windows or just the front?

This is the master switch. It controls the front passenger window and both rear windows from the driver's seat. Passenger and rear doors have their own individual switches.

What if the switch doesn't sit flush after installation?

Test-fit first before fully seating it. The console opening can vary slightly with age. If fitment feels tight, check that the connector is fully clicked in — sometimes the harness itself needs a gentle nudge rearward. If it still binds, contact support with a photo.