Do you have the original spinner and spinner knob? You can hack the spinner with a mikesarcade trackball adaptor and give you 3 mouse buttons to play with. If you can find a real bright 19" crt, Tempest should look pretty decent, don't even consider an lcd, it'll never look good for a color vector IMO. Mounting the monitor will be fun, I'm not even sure a 19" VGA will fit into the opening for the monitor, if it does fit, it'll be real tight.
Depending how original you want Tempest to play, you may consider an ledwiz for the start buttons flashing and give you inputs for the two coin switches.
I don't know how to do "shelling", I wish there were easy instructions for running guimame...