1) Can I upgrade my screen to 8.8 inch without changing the BMW head unit or iDrive?
Yes, you can upgrade your screen to 8,8 inch with a much higher resolution of 1280 x 480. However, if you do not have navigation in your head unit, it may not be that useful. Original 6.5 inch has a resolution of 800 x 600.
2) What are the differences between Navigation, Navigation Plus and Navigation Professional package sold by BMW for F45/F46?
Business Navigation System package: 6.5 inch screen , Navigation Head Unit (EntryNav), standard iDrive controller and 32GB flash memory (VO code: 6UN)
Business Navigation Plus System package: 8.8 inch screen, Navigation Head Unit (EntryNav) , touch iDrive controller and 32GB flash memory (VO code: 6UP)
Navigation Professional: 8.8 inch screen, Navigation Head Unit with DVD player and 200 GB Hard disk (VO code: 609)
3) Can I upgrade my basic media unit (without Navigation) to EntryNav (Navigation Head unit) on my car?
Yes, you can do it. This will involves updating your MAP(which is based on ROUTE maps) with new FSC code to activate the map and installing the GPS antenna. I am doing some further research on it and will update my result in future postings.