When mine split, I called several car upholstery shops and nobody could give me a quote over the phone. I went to a highly recommended (babblers) shop, Jeda Generations. They do remove the top and sew in a new plastic window. The cost was ~$550. You can opt to have the top replaced if the originals is showing signs of wear, or you could have one of the retrofitted tops with a glass window installed, but obviously more $$.
I know there have been several So. Cal shop requests over on PPBB.com, so you may want to check the archives over there for recommendations.
Good luck!