I assume you know the sensors are bad. Lots of people say to replace them, but I feel actually testing them is a good idea. Below is a link to how you can test them, it is for B5 model but you should be able to figure it out. As far as physically changing it the pre one is real easy, the post one is a little harder because of the longer cable run. I'd say try to do this yourself, it's a pretty easy project.
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