I havnt done a full plexi door any larger then the one on my cresties tank and it works but it's only 10" x 20" so it's not too big.. how big would the doors be? I would say use a thick plexi for the door so that it wont bow on you.
they way I built my doors was just like you would for a kitchen cabinet door. the plexi is set inside grooves in the wood... I'm not sure how handy you are with wood woorking, but to do sliding doors would be much easier for someone who is not familiar with tools.
All you really need is the track which you can get at home stores ( I prefer Lowes) and the plexi cut to size, also some locking system.. what i see the most for locks is the style they use on electronic case in stores.. Ithink reptilebasics.com carrys the locks and track.
here's a few pics of what i did, these where my work in progress pics.
a shot of the door opened. after the plexi was inplace I siliconed the seams to seal it an keep it from movin about.
Cheers