White pearl is fairly easy to paint. Cadillac does have one of the nicer white pearls. You could use mopar white and add any pearl coat. Think about using a different color pearl in the mid coat(blue,red, purple) to possibly match the interior or just to be different.. I would suggest doing a spray out of the color to determine the number of coats to get the color you want. If you decide to change to a colored pearl, have the paint shop use an OEM formula and just change the pearl. I work in a PPG paint store and have done this a number of times. This takes the guess work out and gives you a formula if touch up is needed. $800/gallon seems VERY high to me!!!! That should get you a gallon of the base and pearl plus reducer...If you use one of the mid-tier paints, Shopline/Omni or Nason, $800 should cover all the paint and clear...
Bob