The "oil level" sender is bolted tot he side of the oil pan with two bolts and has one electrical connection. The leak usually comes from a worn out $2 gasket. You could easily replace this gasket yourself. Make sure to clean out the sender unit with some degreaser to make sure the float inside the chamber is as clean as it can be from all the old oil.

As an abundance of caution, I would replace the whole unit with new (comes with a new gasket) and likely never have to do this again. If your shop won't charge you more than $50 for everything, then have them do it.

The "oil pressure" sender is different and is threaded onto the oil tube just below the oil filter. It looks like a small flying saucer on its side with one electrical connection . It's also and easy and cheap DIY job.

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03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio