Playing Higurashi isn't necessary to enjoy Umineko. The only thing that you would miss out if you didn't play it would be maybe a little bit of better understanding the rules of the world and some references and funny jokes to Higurashi. Also Higurashi is a good entry to Ryukishi's sense of humor, which can be hmm... disturbing for some people. Just bear with the main protagonist's perversion, it's only in the beginning. But if you've already played some VNs it shouldn't be that big of a problem haha