I've been there a couple of times. and its very pretty. It 's a free museum, but you have to pay for parking ($10 or $15 depending on time of day). I'm not a big connoisseur of museums, but I enjoyed it. I know that they had to return a bunch of stuff that were found to be stolen and had to pull a bunch of stuff that were found out to be fake.
WRT Hearst Castle, Julia Morgan had to deal with Hearst himself and worked on the place on her weekends while working as an architect in SF. I was impressed they got the water for the place from the next valley over. (no local water well or supply)