[fitchesbass]

OP there are plenty of people that have done what your asking - I would search around. You can retrofit the oem unit into a car without the nav with a bit of work.

As for the sunvisor thing... doesn't sound like my cup of tea. So when you want to get directions you need to have your visor in front of you field of view and stare at it while your are driving. The positioning of the oem unit is at least non-obstructive of your vision and is a quick glance from your normal line of sight out the windshield.