I think it costed me about $75. I had a few other things done (SRS light reset which was $90), and one or two other small things. The total was just less than $200, so it must have been about $75. And they were really nice to not even charge me for the bulbs! He asked me if I wanted to just replace them all, about 22 or 23 of them, but they would each cost $3 or $4 (but this IS the dealer)!! 3 or 4 times 22 or 23 is close to $100! So I said just to replace a few of them, well they replaced them all without charge.
Anyway, I don't think it's that hard for them to do. I do know that the C-class is MUCH simpler in very many aspects than a 140.
You should call your dealer and find out the price. Good luck!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)