A month or so ago, I posted a question here asking if it was possible to retrofit navigation into a non-navigation car regardless of any cost (obviously cost matters to me, but I wanted to know if it was possible and what the cost is). There were some responses which said it was not possible due to all the differences.
Well, I have been researching this extensively, and it *IS* possible to take a non-navigation E46 to fully BMW OEM navigation E46. In fact, BMW provides little known kits to do so which include almost all the parts, harnesses and directions to do so. These kits are still available in europe, but I believe they are discontinued in the US (although some dealers still may have them) - You can't use the euro version in a US car. And if you can't find the kit, you can buy the parts piece meal.
Now the bad news:
#1: The cost of the parts alone is roughly $4000US+. I don't know how much a dealer would charge for labor, but the install manual claims its about 8hrs of work if you "know what you are doing".
#2: You could install it yourself and save the labor if you know what you are doing, but it would still require going to the dealer for reprogramming of various computer units.
#3: It requires disassembling a LARGE part of the interior (drivers seat, drivers door sills, rear bench seat, center console, center dash, rear seat shelf, trunk liners, carpeting, etc.
Sounds like a lot of work and hassle and is likely to end up costing $6k to $8k when its all said and done.
Just thought I'd share this info for those that are curious.