Centipede doesn't use a joystick it uses a trackball. Centipede sideart is reproed and available from several locations, you are going to want to get the REAL STUFF and not a print from mamemarquees.com (they are more for custom graphics jobs, the real prints from the repro places are much better).
Centipede uses a 19" monitor.
Your first step should actually be acquiring the correct cabinet, any converted Centipede, Arabian, Dig Dug, or Kangaroo cabinet will be suitable (these vary ever so slightly in design, but they essentially look the same and the parts swap between cabinets).