Thinking converting my hope pro II / 717 rim to tubeless during my 5min dream time, how easy is it, and how easy is it to change a broken spoke once converted?

cheers.

Unless you are lacking in dexterity, no issue in replacing a spoke IMO.

its not hard to set up and then you basically do it again once you have replaced the spoke, or you can be canny and try to remove and replace the spoke without letting the nipple slip out of place but tbh its so easy i wouldnt bother.

If it's an actual spoke breakage then you should be able to replace it without needing to unseat the tyre. Just hang on to the nipple while unscrewing the spoke and make sure it doesn't fall back in the rim cavity. Re-use the nipple with the new spoke.

Just pull out the Stans (plus cut through any tape) at the appropriate point – replace as normal.

Done it recently. As above, reuse nipple and make sure you don't let go until you know it's threaded properly. Took about 5 mins.

Where did the spoke break?

Yank on remnant of spoke. Jam spoke key on nipple, if it is a bit loose get some tape on the spoke key for a v firm friction fit. Bend remnant of spoke into L shape, unscrew. Insert new spoke through hub eyelet, thread new spoke into nipple, remove tape from spoke key if used, tension spoke as per normal.

Did this on my hack bike on Sunday, took 10 mins, didn't even have to deflate the tyre.