The question is too general. Depends a lot on the kind of surgery you're doing. I guess the answer you're looking for is that anyone could be a surgeon, but not for all kinds of surgery. Also 'basic plumbing' with no room for error is not an easy thing at all.

I'm just relaying what my friend who is studying to become a doctor told me, but by his account there's a wealth of techniques for each procedure or even parts of it, like tying up the dangling bits after kidney removal.

Ultimately it boils down to what a given surgeon practiced in their career.

Most complex or endoscopic surgeries are (dependent on dexterity)

It's more in that if you improperly connect a to b someone dies, and it's not just a snap fit like a pipe. You need to do things like suture two blood vessels together, using pliers (not the technical term), inside a dark box lit up by a tube, while looking at an upside down TV image of what's going on.

It doesn’t have to be upside down; you can just rotate the camera to any angle you like.