Hello, I just bought a Used 2004 LR RR with 67k Miles

Finding it tough to understand the following:

Transferbox Neutral started displaying today = Understood taking to a Mechanic to Fix

However, I see so many parts that I want to replace and it is so hard to find Schematics for the car online. Internal and External schematics. I simply want to be able to identify the parts needed to replace and shop and or buy

As well the Radio does not work, I simply want to replace it and do my best possible to find a "today" receiver that can still show the basics that show up over the steering column in the main dashboard. Normally I am use to taking my car to Best Buy and them installing the radio yet OMG so much was programmed into the Darn receiver that have nothing to do with Radio.

my email as well is ahigdj3@gmail.com

Please HELP.