The gear select needle is stuck at "P" on my column shift 71. How difficult to repair is this and is it worth the effort?

The little cable that actuates the indicator and is attached to the steering column is probably broken. You'll be able to see it's small metal clip and the retaining screw from the underside of the column.
You'll have to remove the instrument cluster and then remove the indicator module to repair/replace.
No too difficult of a job...I did the one on my '72. You will have to drop the steering column.

Thanks for the info Bill!!