So I went around and put the new wheels on and while I was doing that checking all brakes and making sure they're all good. I get to the last one, passenger rear, and it's got a good layer of black greasy gunk all over it and it's even on part of the wheel well. Had the wife get in and use the brake and nothing coming out of it so does that mean it's a wheel seal? If so, is it something I can do on my own?