Hi guys, I was wondering if you guys knew if I could sand down the finish and what grit sandpaper I would need to get the gloss finish on my Epi Les Paul Standard down to a satin finish?

Also, would I be able to work with the contoured top and binding as well?

It doesn't work that way. If you sand it it will just look like you bought a guitar with a crappy finish on it. Satin lacquer actually has a special agent in the paint that makes it not glossy. Even if you scuff up your glossy finish, with wear it will get shiny again and just look weird.
You can spray it with a clear satin. That may work. It works just like clear gloss yet has a low sheen.