My 2005 Armada is having some age issues as well. Turning around 96,000-97,000 miles currently.
Door lock Actuator
Our passenger front door unlock actuator gave up the ghost. I pulled the panel off, and realized I don't have small enough hands to try to un-bolt & un-plug the actuator, so the dealer is fixing it right now for me. $250 parts & labour here too, as previously mentioned.
For approximately the last 6 months or so, I've been pulling the glass latch, to help the rear hatch open. Now I see what's the problem after reading all your write-ups. Since pulling the passenger door panel off didn't scare me, I'll tackle the rear hatch panel tonight, and lube both the latch mechanism, and then the actuator. I'll take picture as I do this, and post up afterwards.
It seems, only one post in this thread had a Nissan Tech recommend lubing the mechanism first (which fixed the problem), so I'll assume it's just the weather/rust environment of the "Great White North" that plagues this latch.
I'll drill a hole in the actuator and fill it with some "Fluid Film", as I have some in the garage, but only after I verify lubing the latch parts fixes the rear hatch problem first.
(Of course, if it doesn't fix it alone, I'll lube the actuator, and post up my findings.
Thanks for all the great commentary.