Piston repair

What is your question?

I drive a volkswagen golf 2.0 mk4. I believe the pistons need to be replaced. Or, at least the piston rings do but I think I would rather replace the whole pistons even if that's the case. How long do you think it would take for me to do so? I'm not an experienced mechanic whatsoever, however, I can be pretty handy and enjoy learning technical processes as needed like this. I've already changed spark plugs along with wires, coil packs, cleaned fuel injectors, etc. I am pretty much looking forward to do the repair myself. Also, the gaskets that I come across, timing belt and whatever else may be of interest. My received codes are P0300, P0301, P0302 and P0304 Thanks in advance! Micah-

What makes this problem better or worse?

The engine is extremely loud and rough idling. Major oil consumption, along with multiple and constant misfiring.

How long has your 2003 Volkswagen Golf had this problem?

1 month approximately.