There was a similar discussion just a few days ago. Look in the fix it forum or do a search on broken cable, lift, etc.
That might be me. The same cable, same corner, broke on my pup friday afternoon. Luckily, I was in my driveway. I couldn't get that corner to go down though. http://www.popupexplorer.com/forum/index.php?topic=78500.msg163854#msg163854
Between work and kids scheduals I don't have time to do the work myself this week so I brought it to a place recommended by other shops. I asked him to try and have it done by wednesday evening and he said that it probably wouldn't be a problem.
Anyway, if you look at the Coleman lift manual, http://rvworkshop.com/Coleman_Lift_Systems.pdf , and your handy, you can probably do it in a few hours. Other guys on the forum have gotten the cable and crimps from hardware stores and Home depot. Alan