First off, that
PDP-11 is a genuine antique and a nice piece of history; don't wreck it.
Servo motors and Jaguars are not a good mix. You really want a servo motor driver, one that can manage the feedback from the encoders. I also don't think it's easy to run a CAN bus from a typical PC.
My best recommendation would be for you to google "servo motor" and learn how they work. Also, it is a lot harder to build something (like a 3D printer) from components you happen to have, as opposed to buying what is best for the task.
Lastly, get a copy of issue 21 of MAKE magazine.