shift cable adjustment

Does anyone have detailed instructions on how to adjust the shift cable. My 96 S10 has suddenly decided not to go into park. THis happened once before a year ago and the dealer adjusted the shift cable.

The bigger question is why is this happening.

I have located the cable under the car but what little instructions I can find say to squeeze the clip and pull the cable forward. While I can find the cable, fiding the clip is another thing. (I also have the service manual and am still confused)

I can reach under the truck and push the shift level with my finger and have it go into park.

Last time this occured, the dealer adjusted the cable and gave me back "P" at the expense of losing "1". (I told dealer it was a 12 yr old car and not to spend too much money on it). Does this mean the cable is stretching and needs replacing?

iff there is no more ajustment left in it you may have to replace the cable.