There are probably lots of techniques to do this, but one way is this:
Since you know you want the audio from the closeup camera, drag the clip(s) from that camera onto the timeline onto the first video track. This should give you the video and audio from that track.
Now go to a clip with one of your other camera angles in the media pool or explorer view. ==RIGHT CLICK== on the clip and drag it onto the second video track. When you release your mouse from the right click you'll have a choice to add the track as "Video Only - Add Video". Choose this and you're off and running. Just align them so that the video is in sync with the audio from the closeup camera.
Now, to alternate between the shots, you can just split and cut out parts from the 2nd (top track) clip which will let the video from the closeup camera "show through." Rinse and repeat for the 3rd video track.
There are many methods, but overall this is pretty easy. It's a lot easier if all the cameras ran constantly for the entire event because then you only have to syncronize them once. It's not difficult if some of the cameras paused during the wedding, but it does take some time to resync after each pause. So, if you haven't done the recording yet, make sure you tell your camera operators to never pause during the event!
What i would do is to put the main camera's video on the bottom video track and it's audio on the first audio track. Add the other camera's video to the overlay track and it's audio on the second audio track (this should happen automatically when you drag it to the timeline). Zoom in close enough so that you can line up a peak in the audio between the two tracks and get them syncronized, then delete the second camera's audio track.
Find the spots where you want to switch back and forth between the cameras. Split the second video track at these points and delete the video where you want to see the main camera. This works because video clips on higher tracks hide lower tracks. You can add fades to the edges of the second video events if you want to crossfade.
That is about the easiest way to do it. You can even put a third camera on the top video track. if you do have three video tracks you'll have to cut away both of the upper tracks to see the bottom track.
You might be better off muting the unwanted audio rather than deleting it (at least in the early stages). It makes it easier to regain synch if you lose it, plus you might find there are things you want to include from it - at the last wedding I went to, the choir were at the back of the chapel and the priest began talking to the congregation half way down the aisle.