So, if | is used for :, what's the meaning of : within a URI? I know it's used to separate the original service name from the rest, but don't recall any special meaning on the right side.

I don't think it has a special meaning, but it's a reserved character for the entire URI. And yes, many browsers will let you get away with using ':' instead of '|'.

And what do you do about |'s in the name that were there to begin with?

You beat up the person who named a file with a '|' (:

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Reinvent a rounder wheel.

Note: All code is untested, unless otherwise stated