Barn doors not locking/unlocking

We recently purchased our first Sub, a 1998 K2500. One of the few minor things that need addressed is the fact that the power lock isn't working on the barn doors. When I press the "2x" button on the remote I can hear a "click" under the dash but nothing else happens. Also, if I use the power lock button inside the rear doors it only locks/unlocks the front 4 doors. The bottom line is that you have to use the key to lock or unlock the barn doors. Even so, the lock is very stiff to turn. Is it probable that the actuator needs replaced? If so, is this a difficult task?
Thanks in advance.

My burb is of the older body style so is set up a bit differently but I believe that power is delivered to your back doors by a set of "fingers" that make contact with corresponding contacts on the door jamb. I'd start by cleaning those up and see it your issue is perhaps just grunge. As far as the door lock actuator I haven't been into a set of doors like yours but typically once you get the door panel off they usually aren't too dificcult to take care of. It's also possible that you have had a connecting rod come loose: they are held in by a plastic clip. Have someone else toggle the lock while you are at the back door can you hear the actuator move? If you are reasonably handy I believe this is a job you can do.

my 95 burb has been doing this for about a year, the problem is like you said "stiff to open and lock with the key" I belive the lock just needs to be lube up internally, Ive sprayed wd40 into my key hole and the lock mechanisim, and it will work sometimes, about 50% , it just needs to be opened up and greased well, I think.

but also my contacts on the back doors, need to be well cleaned also, I will try that soon! thanks for the tip.

You know, those contacts ARE pretty dirty now that I think of it. I noticed yesterday that the rear defogger didn't work, either, and I wondered if that might be the reason. Just didn't have time to check it after work since I was late getting home.
When I locked/unlocked the doors I couldn't hear the actuator so it's most likely not the plastic clip issue. Gotta check it out tonight.