I don't see your filter info in your signature, but in general, shop online first and compare the "Push/Pull plunger/piston repair kit costs to a complete new one. I saw a Hayward kit recently for just over $50, while the entire assembly was only another $26. For Pentair, one repair kit was $50 versus $90 for the entire valve assembly.
To replace the whole valve, it will need the piping work. I'm not sure if I can DIY, though I have some kitchen sink piping DIY experience.
If just o-ring or the plugger need repair, it will be much easier to handle myselves.