Been there--done that.
I replaced the cable about five or six years ago and as I remember it the job really wasn't that bad once I got the boat jacked up off the trailer. That took the longest because I went slow and made sure I didn't do any hull damage. I used hydrolic (car type) jacks with 2 x 8 wood blocks to spread the load over a good section of the hull and I then slipped in spacer blocks between the hull and the bunk boards just to be safe. I think I only needed to get up about 5 inches or so before the attachment point on the aft portion of the swing keel was within reach. (You don't have to raise the entire boat, only the stern.) After that it is just remove, (remember exactly which way the cable was routed up through the tube-there is a right and wrong way to do it) and replace. Total time could be as little as 2 hours but a better estimate is 3 to 4 for the first time you do it. Think twice, act once!! Good luckMichael