99 740iL currently sitting without nav.. Just curious what OEM nav can be installed and function properly in the 99 e38. what would i need? (drive, screen, antenna?) any additional wiring harnesses i would have to purchase?

www.e38.org for the retrofit PDF

PDF shows everything you need and all the tools required to install it.

just a quick run down-

Nav screen
dash bracket
wire harness
gps antenna
nav computer
trimble (for MKI and MKII)
trunk mount radio
trunk nav brackets
trunk nav trim
ibus CDC

I've been doing a LOT of traveling lately and using rented cars. Since I was in unfamiliar cities, I opted to add one of those Garmin portable GPS systems to my rentals. I'll never go without Nav again. At home, when I drive my 7, I don't get to use it much because I know where I'm going. It really comes in handy when you're in an unfamiliar place.

Which is a long way to say that you might take a look at some of these portable units. I just bought for my work (got tired of paying daily rentals for a unit the size of a softball that I can easily bring with me). I bought a Garmin Streetpilot c340 for $260 delivered. You'll pay that much just for a set of CD's for the OEM unit.

I am forced to reluctantly admit that the Garmin is much easier to use than my OEM Nav and it includes the map for all of U.S. and Canada built right into the unit. While it is not built into the car like the OEM one, it is fairly attractive and can be moved from car to car as needed.