Sum, walk across the street and look at the non-driven wheels of most any semi tractor, and probably the trailer wheels, too. It's very common to have "wet seal" bearings on 'em, and they usually have a transparent plastic cover with a line scribed around the face and a center hole with a rubber (?) plug. Visual inspection of oil level is a 2-second task, and adding some lube requires nothing more than pop out the plug, add some goop, and put the plug back in. one quick look and you'll see if you can adapt the concept to your racer.