Obviously, I’m a total newbie…

I just bought a X5 4.4i 2001 (E53) with NAV and it looks very old and tired. What is the most current OS version that I can upgrade to…V31? I have MKII (s/w 2 – 1/31). I can’t seem to find a working link to download it…Is it as easy as it seems…download to CD, turn key and pop it in and cross fingers?

Lastly, I’m planning to upgrade my screen to the 16:9 this summer…should I wait to upgrade OS till I install new screen or doesn’t matter?

Thank you in advance.