I just did this on my in the water 23' a few days ago. Save yourself some $ and DON'T get the replacement pendant from D and R marine, which I did, and ended up removing anyway.
Get yourself a pair of swim masks from Walmart and jump over the side when the boat is tied up at the dock. It is not difficult to swim underneath and get the pendant line. My line was hooked up, via shackle, to a 3' pendant wire that is attached to the centerboard. Remove the shackle, and thread a new line to the old line in the cockpit. I used only 1/4" line that I had lying around, if you think about it, there is not a lot of weight needed to lift that fiberglass centerboard when it's in the water. Pull the old line through and just TIE on the new line with a round turn and some half hitches. DO NOT use a shackle, because I believe that is why my centerboard is always getting stuck when you fully retract it into the keel slot.
The whole process should take about 30 minutes. I needed about 10 dives to do this. You also might need some sort of weight added to minimize your buoyancy. I did this when the sun was at it highest to illuminate under the water, but I also have an underwater head lamp that helped illuminate the pendant wire and the new knot.
Think of all the $$$ you will save by not having a boat yard do it. Plus, you will be like a real McGuyver by doing it yourself. Good luck!