
Andersen Windows & Door Lock Cylinder, Sliding Glass Patio Door

Take a look at the our 82-319 key cylinder, made for the right hand side (when viewed from the outside). I believe this is the part for your door. It comes with directions for the installation. As for tools, other than a Phillips screw driver you will need a drill and drill bits.
It sounds like it could be an issue with the mortise lock. I recommend checking that for any signs of damage. You could also try manually throwing it; what I mean by that is, remove the lock and then try to turn the mortise with a screwdriver. If you run into the same issue, then it needs to be replaced.
My recommendation would be the 82-037, assuming your door is the same as what's pictured above.