1) matching numbers means the VIN sequence numbers match the cab, frame, engine, etc. Basically it means it is just like it was when it was sold and nothing is different. As far as trucks go, I see absolutely no point as they are never going to be a hot item like a Corvette or Musclecar.
2) For a "Decent" 20 foot paint job, expect to pay around 3000, for a show paint job with no perfections, there won't be a number, but you could probably tripple that cost and be close if you want it flawless. Generally you can get a great paint job for around 5000.