How to remove the lock cylinder for trunk??

Most locks are held in place by a big U shaped spring clip. Remove the plastic trim covering the lock, pop the clip loose that holds the arm on the lock. Then pull or pry the big U clip off, and then the lock assembly slides out.
 
There will be a rivet you will have to drill out of the retaining bracket. If you lift your trunk open you will see it under the lip of the trunk lid.
My '91 didn't have a rivet, maybe somebody got there before me :rolleyes:

It's a pretty easy task, I even went so far as to "re-key" the new cylinder to accept my door key :D