New to an '05 X5 - Nav questions

[romaj12]

Hello all,

Just purchased an used 2005 X5 4.4i w/Nav + DSP. Searched the Navigation forums, but am really totally lost with how to upgrade.

A few questions I have:
1. What's the best way to update the firmware on my MKIV system?
2. What's the latest Navigation DVD's available for my system? Is purchasing from the dealer best?
3. How can I easily change the splash screen on the LCD? What are the pixel dimensions? Not sure if I really want to go through the trouble of NavTweak software or not.
4. My Nav DVD drive had the DSP cable plugged in the back. I am installing a CD changer (which was taken out of the vehicle), and I know the DSP cable needs to go into that, but why was it in the Nav drive?

Any help, I'd appreciate it!

Jeff

[romaj12]

I also understand that some of this belongs in the Navigation forum, but there are so many posts under different models, searching took forever. If you can direct me to a current post you know of that would be helpful.