I think your fears are well founded....
I'm assuming that hauling the boat is going to set you back a couple hundred and you'd rather just do it once so I'd suggest you bring some extra hardware, even if you have to buy it. I changed my pendant by persuading a friend with a wetsuit to free dive (no tanks)on my 192. The shackle I got from Rudy might have fit had we been able to get the old shackle off. The nice, forged Wichard shackle from Rudy was not wide enough to fit around the stamped steel one that was attached to the centerboard. From my "boat junk" box we re-shaped a short stamped shackle to attach to the existing one. Don't forget to fashion a messenger line and attach it to the old pendant which you'll pull out the bottom. I seized the messenger line (1/8" dacron) to the pendant with whipping twine and then had to kind of "streamline" the joint with tape to get it to go around the first corner when we were pulling the new pendant up.Best of luck, you'll feel better when it's over!