Hi Doug the build coming along very nicely now the neck is set !
I've removed the plastic cover of a PBG P90 pickup so not sure about yours, I would think the plastic cover is glued onto the pickup. Maybe apply some mild heat to the cover and see if the cover can be wiggled and removed from the pickup. Don't force it. I'd say the 2 phillips screws on the back are internal mounting maybe for the pickup bobbin