Tappets S40 T4

[Slomo]

Hi all

I believe ahve got Hydrolic Tappets in my S40 T4 1999. Some of them are becoming noisy? Should I replace them? If replace do I just replace them or can they be upgraded? Bit of a noob with Tappets as I ahve no clue :(

Any ideas where is the best place to buy them?

Slomo