Did they just give you a DVD or something? If so then you need some kind of video "ripper" (to convert from disk to file). Not sure what's good for Mac's but there's probably lots of options.
Once you have it online, your video editing software shouldn't be too hard to figure out and you can then concatenate them together into one video or whatever. I used Windows Movie Maker on a PC for a few videos and it wasn't too bad to figure out, and Macs are said to be much better for video editing so you should be able to figure things out.
I just upload videos to youtube.com and they show up on facebook because they're linked. If you want facebook to host the video then you have to upload it to there. I can't imagine the process is much different from pictures but I haven't tried it.
Neat stuff, where did you jump?