Rob you should be able to get bolts or what ever in that line in local hardware.
This link has a slide thread that I just put together with one
thread on what your involved with that may help you, that slide thread is in
this one.
The rubber gasket is suppose to keep rain water out of box when slide is out, should be better than the old ones you have now.
The Actuator can be replaced but some people have cleaned the contacts on it and removed the rust, if a 12v lock does not function for allowing slide to operate a gentle tap on box may clear the contact of Actuator to operate.
Good luck in your maintenance problems.
Enjoyed your area back in 2000 great area.