I just bought...
 

A 2011 m sport pack. no nav, no pre pkg.
I want to have factory nav installed. is this possible?
If not, are there any after mkt systems that integrate into the pre existing wiring?

Yes, you can retrofit the factory navigation system. The E38, E39, and X5 all share the same audio, video, and navigation systems, and except for the brackets, the retrofits are pretty much the same. (The E46, and E83, and E85 also share many common components.) There are many well-documented retrofit example projects here in the FAQ pages as well as on the Bimmernav Navigation forum (The Navigation A/V Forum). The hardest part is running the navigation harness from the trunk to the dash. Otherwise, it is pretty much plug-and-play after the harness is in.

no pre wire huh?

Nope, no pre-wire.

The major differences are:

1. You need to add the set of wires that run from the nav computer in the trunk to the in-dash display that carry the video signals and audio from the tape deck.
2. You need to re-route the radio wiring harness from the dash to the trunk next to the battery.

This was a common post-sale project. BMW used to offer a factory navigation retrofit kit that had a cool adapter harness that routed the radio wiring to the trunk and was bundled with the screen video wiring. That made the installation much easier. However, I do not think that kit is available any longer, and it was expensive compared to buying an original navigation harness.

2011 car would be iDrive and a huge amount of money plus coding and dash work.

Oops... I overlooked that it is a 2011. Yes, much more difficult. Fewer examples in the world of those.