Marantz 2240 B Maintainance

I have a Marantz 2240 B receiver that seems to be in very good working condition, which I've started cleaning and have 2 questions about. First, I have removed the front panel screws in the 4 corners. What else is holding the front panel on? There seems to be something anchoring it right in the middle, around the "mids" tone control. Secondly, how do I clean the balance slider? Is it OK to just spray a cleaning solution into it? Thanks for your help!

Dale.