Painting a Certificated aircraft, and other questions

[geosnooker2000]

Hey guys.
I just have a stupid question. I'm sure there is a logical answer, but why is it important to the FAA for an A&P to be the one to paint an aircraft? Are they worried about the weight of the new paint? Corrosion protection?

Also, I am given to understand one does NOT have to get new upholstery signed off on. Seems like that would be a lot more opportunity for messing up weight and balance calcs.

From a practical standpoint, do people replace, for instance, landing lights (bulbs or replace the whole fixture) without getting an A&P to do it? How much could it/would it cost to get an A&P to replace a landing light on a 1965-ish Piper or Cessna? Like, if you wanted to switch it out for an LED fixture?

[Bill Berson]

An aircraft owner can do anything listed in FAR43 appendix A (c)
It is called Preventive Maintenance. Refinishing is allowed with the exceptions stated in the rule.

[Kyle Boatright]

In the big picture, you can repaint the airplane, but if you pull control surfaces off (for instance), you'll need a mechanic to (legally) reinstall them, balance them (if necessary), etc.