My nav screen is white and my radio volume is low. I have a 2001 RR HSE from the US. I want to know what to do to Fix it. I have read to check fuses but which do I replace or check? Or what to do. I also want to know how to completely discharge the capacitors or voltage. HELP!!

If your sat nav drive has given up the ghost it will take out your volume, including steering wheel controls. Did you disconnect the battery recently. The sat nav needs a couple of minutes (until the red light on the drive goes out) before disconnecting.
In the short term you can disconnect the sat nav drive to get your volume controls back.
Sorry i cant help with sat drive it'self, i'm sure another member will be along to advise.

Sat Nav computer is u/s. Disconnect the plugs from the rear of the unit and radio volume should come back to normal!