I want to disconnect the (original) power steering return line so as to do a thorough flush and fill of the steering fluid.. Both ends of the rubber line are clamped to a hard line with what looks kind of like the type of clamp one would see on the boot of a CV axle (neither a worm gear nor a spring clamp). How does one remove this? Figured I might as well replace the hose while I am at it. Can the new hose be just the rubber part, or does the replacement line need to include a portion of hard line on one or both ends? If the former, can it be attached with regular worm gear clamps?

I couldn't speak to the factory clamp, but the PS return line is under no real pressure and can be clamped with a regular clamp generally. And I'm pretty sure that you can just replace the rubber hose if needed (I don't recall the stock one on mine, I used the donor pump and line from the 5.3, and I believe it was a spring clamp that came on it).
The PS feed line, however, needs to be treated with caution, properly crimped, etc. but I'm sure you're aware of that. Just making sure future lurkers don't get things confused.

What Shawn said above!!

As Shawn said the return is very low pressure hose and a worm clamp at each end should work. But be aware that there is a specific hose made to be used with P/S fluid. A good parts house should be able to sell you a length of it. 3/8" rubber fuel line is not the correct rubber to use. P/S fluid can get very hot.
https://www.sae.org/standards/content/j189_201207/ Gates, and i think Dayco make P/S hose to that spec.

Also it you check Rockauto the entire hose with the steel end can be bought. Edelmanm is good stuff.
Bob