mornin' tesla!
well, that small robot looks like it could easily be turned autonomous...
although it would be a tricky bugger to solder, you could use something like an attiny2313 or smaller to control it.
something like the l293D could be used as a dual motor driver...
by infared rangefinder. do you mean sharp ir? this may be too big for the robot and make it flip, maybe think about something smaller like a infrared emitter and detector pair...
overall, i think this is a totally achievable project!