Does Galle Fort close at 5 PM? And where do we buy tickets?

We are arriving in Galle quite late tomorrow (around 6:00 PM) after our safari in Yala. We really want to see the Fort, but I can't find the official ticket price online.

Does the main gate close at sunset like Sigiriya? Is it worth going inside in the dark, or will everything be shut? We only have one night.