Hydraulic lifter replacement 'how to'?

I suddenly have a very noisy hydraulic lifter. I have fresh engine oil and filter and added some hydraulic lifter ease oil additive which did not clear up the issue (1992 mk1 Cabrio DX engine)

I am thinking that I will probably have to replace the lifters, but surprisingly could not find much in the way of 'how tos' specific to Golf mk1/2s. I have only worked on solid lifter engines before.

Is anyone aware of a guide or can give some pointers?

Also, the cam has no obvious wear, but it looks from what I could find like this will have to be replaced in pair with the lifters?

https://www.cabby-info.com/files/engine/CleaningHydroLifters.pdf

Thank you so much. I also found a guide to replacing the cam and lifters on that same site. https://www.cabby-info.com/files/engine/ReplacingTheCamshaft.pdf

I will try to clean my lifters first, but I also have a set of new lifters. So I just want to check, if I have to replace the lifters with new ones, do I have to replace the camshaft with a new one as well? I read that the cam and lifters wear in together and only replacing the lifters can cause excessive cam wear (general info I found, not mk1 specific). But I'm not sure if this applies in all cases.

In the how to clean the lifters guide posted above, the wear marks on the lifter gets removed with fine sanding paper, so there will be new wearing in I suppose.