There's probably a simple answer, so simple that I can't see it.

I have imported 60 minute VHS video to a .mpg file.

How can I break it down into constituent shots and save each shot, so that I can re-assemble a newly edited version of old holidays?

Well, there's more than one way to skin a cat as they say....

Personally, if I've got one long file I want to split into separate scenes, I open it up in the trimmer window and mark each shot as a region. I then run a "regions to sub-clips" script.