The halyard should not be stretchy. Get 75' of 3mm low stretch line to replace it. All the major manufacturers of cordage make it.
If you go to www.hallspars.com
, they have some of the best hi-tech cordage that you can order on-line.
Usually, the problem is getting the ring on
the hook, not off.
If the sail came out of the track at the top, there is an aluminum piece that Hobie makes to replace the last 10" or so of the CompTip track. (LUFF TRACK UPDATE Part #50404111) That's the first thing to do.
I always used an Aussie Halyard ring -
They just work better.
When you're trying to disengage the halyard, hoist the main up as high as you can, then rotate the mast counter-clockwise (have someone pull the rotator arm to the starboard side of the boat). That gets enough separation between the ring and the hook so that the sail can come down.
If you can't get the sail disengaged, remove a wing from one side and flip the boat over on the beach to get the sail started down. As you already know, taking the mast down with the sail still on it is awkward at best.
Good luck and enjoy your new toy!