Ok, I guess I am the first one who has completed the installation of the video interface and camera, so here are couple of things that I would like to share with everyone:

1. The video interface has excellent build quality and comes with all necessary cables. You might need to solder and attach longer cables to the interface CAN wires or else it will be difficult to connect the interface to the BMW CAN wires.
2. The BMW_PIP.pdf documentation shows that the interface has a wireless remote. But actually the interface comes with a wired keypad that can be used to change any settings if necessary and then can be unplugged. You'll hardly ever need to use the keypad again!
3. There are some mistakes in BMW_PIP.pdf, so while making connections, be extra careful.
4. There are couple of permutations/combinations that you would need to try with the DIP switches and modes, etc to make the whole setup work. It took me almost 2 hours after making all connections to finally get it working. Sometimes the video would show up, but iDrive would not work, sometimes the steering wheel controls would not work and sometimes it would just show a black screen.
5. The eBay camera has built-in parking guide lines (blue color lines with distance in inches), so you'll need to turn off the parking guide lines superimposed on the video (colorful lines) by the interface. If you need to disable camera's parking guide lines, then just cut the blue wire in the camera.
6. I installed the video interface behind the CD player (below the vent). There is a good spot for it there, specially for those who have a CD changer in the glove box. I actually have a crossover for my aftermarket speakers behind the glovebox, so could not fit the interface there.
7. I supplied 12V power to the camera from the reverse taillight using a relay, so that the camera gets powered on only when the reverse gear is engaged. Connecting the camera to anything else might result in the camera receiving power all the time, which is not a good idea.
8. The delay between engaging the reverse gear and the video showing up on the screen is about 1.5 seconds (I used my iPhone stopwatch to measure it). I don't know if this is better than BMW backup camera system's delay.
9. The toggle switch is optional and is used to switch between different video sources. This can be done using the down arrow on the steering wheel, so the installation of this switch can be skipped.
10. This is more relevant for people who are getting the eBay camera: The video quality is acceptable, not too great, but not bad either. I still have to do some more testing in daylight, but night time performance was descent. The build quality is amazing and it blends perfectly with the exterior. The camera has a glossy black finish and doesn't look aftermarket once installed. I am glad BMW provides a spot for it in the trunk hatch so that we don't have to cut out the metal sheet or drill any holes.

...and finally, thanks us_matrix for taking the initiative and getting this done. Your documentation was extremely helpful! I could not have completed the installation without it and I was extremely impressed with your superfast responses to my emails!