Reddit reviews 100Pcs M3 x 0.5mm 304 Stainless Steel Self-Lock Nylon Inserted Hex Lock Nuts, Self Clinching Nuts

Nyloc nuts.

Absolutely not necessary (really), but I also bought new screws that are a little harder and the hex socket is less likely to deform.

Also not necessary, but nice to have is a miniature metric wrench set.

As I said, it's not hard, but does take a couple hours. Go slow, take a break if needed. There's a video somewhere on youtube of someone doing this which should alleviate any concerns about the difficulty. Remember, if you do this, you're obligated to post the before and after 7x7 bed level image from Octoprint.

I bought these: https://www.amazon.com/gp/product/B075ZZW7VL/

The whole printed extruder assembly, ABS print cooling shrouds, extra nozzles.
M3 screw kit.
M3 square nuts.
M3 lock nuts