(normal day use is $5 to park, I'm not sure if you have to pay for day parking and overnight parking together, probably not)
The office hours I think are 9am to 9pm there, if you arrive after just pay in the morning. They aren't strict or anything.
For camping spots, just drive around on the gravel road until you see somewhere in the trees you want, many spots already have rock circle fire pits, you can drive off the road a bit if the trees have a big enough gap. They have a wash house, bathrooms and showers, I don't think the showers cost or anything. I'm not sure if the camping areas themselves are only primitive or not, but last time I stayed it was, minus the bathroom building not far off.