Upload & Sell: On
I do this all the time and have been doing it for over thirty years. It's not hard but just takes a little discipline to do well.
This is one of the very few areas of digital photography where a light meter actually matters and let's you get your lights even across the area of the art. You'll be doing well if you can get within about 2/10ths of a stop across the art.
The general wisdom has always said to have two lights at a 45 degree angle to the art, on either side of the camera, but what you really want is NO MORE than a 45 deg. angle from the edge of the art that is closest to that light. That actually puts the light at less than 45 and more like 35. If you don't do this, you'll end up with unwanted reflection when you least expect.
If the artwork has any kind of reflection it's almost always a good idea to polarize both the lights and the camera lens, and even when you have non-reflective art, it's often a good idea, so that's should be on your shopping list.
I almost always (unless the piece is too big) shoot straight down on the art. Of course, I have a 12 foot Cambo camera stand with a three foot sidearm, but shooting down is by far the easiest way to make sure your camera is parallel to the art. I used to use a level, but now I use and iPhone app called Clinometer, which is faster and more accurate, always with you and only costs a couple of bucks.
Since I shoot with Canon, I'm also often using the 90mm TS-E lens and using the shift feature to stitch multiple shots together for larger files.