Welcome
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Sorry I'm not that familiar with the U.K. Registration system so I don't know what year model a 57 plate is?
The reason the year is relevant is that on some early cars the fuel pump has a banjo bolt on the bottom.
The bolt is hard to access and requires a triple square bit (which you will need a set of anyways now that you're a proud VW owner
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) to remove.
If your pump has a banjo bolt changing the cam follower could take 35-60mins depending on the size of your hands, the degree of your patience and a good dollop of blind luck
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If your pump has no banjo bolt it's WAY easier and some people (not me cos I'm a cack handed numpty) can change a follower in 10-15mins
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Either way it's definitely a DIY and it's not too daunting at all. Some good YouTube vids you could have a look at.
HTH
Dave