Why do people always send people asking questions here to other sites? There are some super smart people right here at DP!
First of all, congrats on the find -- free is always a score.
If the problem with your joystick is just the microswitches, order some of those. You can get those for pennies vs. a new joystick for $30+.
Replacing the whole side panel is pretty unlikely. Is that formica stuck to wood? You could probably use some wood filler on those scratches (and the corners) and repaint the whole thing.
Textfiles.com has the manual for your game online. Download this PDF and check it out. It has all the dip switches required to put the game into free play.
http://pdf.textfiles.com/manuals/ARCADE/S-Z/
Congrats again, and welcome to the club!