2005 Prius with JBL+NAV system, how to upgrade?

I have a 2005 Prius with JBL+ Nav system, and I would like get rid of the old cassete/cd player and install a new unit or do a stealth install, whatever is better for the system; I have done the install of new head units in a couple of cars before, very basic ones, so I have a few questions:

1)What kind of harness do I need to buy?
2)How do I keep the wheel controls, including bluetooth working?
3)How do I keep the MFD working after this install without loosing other functions?
4)Can I use the microphones that are already in the car for the new bluetooth system?
5)What is the easiest instalation method?

I have a Pioneer and a Kenwood unit from my other two cars, the kenwood has bluetooth and USB input, I don't mind taking things apart, but I would prefer not to split cables, so I am looking for the best possible harness, to make things easier and faster, please advice, thanks.