I had the same problem and you can read my thread at http://www.rvforum.net/SMF_forum/index.php?topic=21387.msg217827#msg217827. Part of the thread has this from me:
"I did not have to remove the sides. I opened the camper and held it up with a 2x4. There are two nuts inside the top of the lift bar. On the bottom, there are 4 nuts to be removed which you can see under the camper while looking in the frame. Then you have to get the top lifted ALL THE WAY and slide the lift bar out. Due to the cabling, you'll notice that the sliding pieces bunch up the cables if you're simply sliding the parts in and out. Keep tension on the bottom wire and let gravity help you. Kinda weird, but you'll know what I mean if you ever have to do this repair.
Well, the RV store sold me the wrong cable (as I said earlier). When I told them what happened, this one fellow said, "Well, you can stand inside and hold it up." Not the answer I was looking for. The parts guy said to get 5/16" cable. I didn't even process that is almost 1/2" thick! So, like an idiot, I drove from parts store to parts store, looking for 5/16" cable until I finally found it and said, "Wait a second..." I called the RV store and he says, "Oh yeah! I meant 1/8"." 1.5 hours later.
I bought 20' of it for almost $20 less than the original (wrong) cable. Unfortunately, the original cable has a threaded stud to put the washer and adjusting nut on and my makeshift cable does not. I estimated the length with the camper open and completely closed - closed works better. I crimped two lead crimps (?), one on the cable and then one behind it with the cable looped through.
So, if you ever have to replace a main cable, it's not too difficult once you have the correct equipment. If anyone is searching for lift repair in the future and needs some info/help, please feel to IM me and I'll help if I can. Locals may even get a free house call to help out."
Best of luck and give me (or anyone else in here) a shout to help with any questions. You'll be amazed how simple this repair really is... once you've done it.