Camera Tracking Question, help me please

[tfandango]

Guys im kind of desperate, my boss asked me to do create an animation using camera tracking. Im more of a modeling guy but the job was great and i wanted the experience, and i was handling everything in a smoothly but i dont know how do this. I wanted to present the scenario and id really appreciate some help. He wants me fuse a 3d animation with the footage of a structure. It is very much like this one: http://www.youtube.com/watch?v=KwsOs...eature=related
skip to 2:00, you dont need to watch the beginning of the video, my plan was to approach this in a similar way as the video, model the area with the new road and its close surroundings and then use an animated mask on after effects to make the new road appear on top of the existing footage, the thing is: how should i approach this? how can i camera track a moving camera through such a long video where everything is constantly changing all the time, i dont even know what should i track, the camera? the road? im really lost here, im sorry for bothering you with this i just want some light into this situation. I dont know how do approach this and how to model in a way so as to follow the video. should i use pftrack? pfmatchit?