if you've got the room I'd do it with the chest freezer & a new thermostat, then its really just a matter of making sure you dont drill through any freon lines.
the mini-fridges are cool but expensive, i built mine out of an older fridge (one with the old alum box freezer that's not seperate) by tearing it to pieces and using a much smaller cabinet with tons of insulation and some plastic to keep things really air tight.
there's nothing too complicated about the whole thing, just follow the old carpenter's rule, "measure twice, cut/drill once" and make sure you know what you want it to look like & where it should fit before you go gung-ho