Make sure to spray a bit water before letting your GPs roam in the cage. The little water will crumble the pellets into smaller, softer pieces. Found that instructions when I looked online for whether or not that bedding was good. Apparently thats how they prepare it for the GPs, and horses.

Some people just get the deworm drops that you can put inside their water.

As for vet fees for deworming, I have no idea. I'm no vet.