I’ve heard you need a permit to get into the park. Is that correct? If so, where do I purchase that and how much is it?

Yes you do need a permit. You need the Northwest Forest pass you can buy a day pass for $5 or the year pass for $30 I think. I use an app on my phone when looking for trails. It's called AllTrails. Super helpful.

Check online. All info there

No permit, but you do have to have a parking pass.