How should I handle them when converting the post to a tutorial?

There is no "converting" :) leave original intact and

Start a new node (reply ok) with "RFC: Advanced techniques with regex quantifiers" in title

Make it into a good tutorial (clear purpose, clear example, clear caveats , clearly digestible ... )

Advertise in chatterbox, get commentary on it, improve/revise

If you've got positive response, post (minus RFC in title) under Tutorials and wait :)

See How does editing work in the Tutorials section?

Compare to these examples both short Common Regex Gotchas and long Parsing with Regexes and Beyond

Also avoid <readmore> tags in tutorials, its visual interference :)