Like the others have said, you need to support the engine with a jack or axle stand, remove the front engine mount bracket to get to the sender which is mounted in the cylinder block.
If your using a genuine sender to replace it with then its just a case of swapping the sensors, if you go for a cheaper, non genuine sender, then there is a sleeve on it where the sealing ring is, if you do not move the sleeve and put a bit of sealer on it, when you fit it on your car, it will leak oil everywhere, like I found out, and had to do the job twice on my car
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Its not to bad a job, just a bit fiddly to get too.
Jochen.
