Since you are not intimidated by the repair, continue to carry your spare cable. You may be able to get enough slack in the cable to check it periodically. Shift to the largest cog. Then, w/o turning the crank, shift as if you were going to the smallest cog. The derailleur should stay under the large cog and you should have enough slack in the cable to pop the last piece of housing out of the chainstay stop. Push the slack inner wire toward the shifter a few inches and you should be able to see the vulnerable section. I may have this backasswards but try it.