I'd try and get a left-handed guitar Sass, although they are thinner on the ground they are available - places like GuitarGuitar generally have them.
Especially so if you are after an acoustic because the saddle is angled so that the bass strings are slightly longer between the saddle and nut (at the top of the neck), which is needed for proper intonation - reversing it isn't ideal, since even if the open strings seem in tune they will be less 'in tune' when played further up the neck. I'd imagine that nylon-strung guitars are similar (I don't have one myself - nasty horrible things
)
Get a Snark tuner (about £20) - they are handy wee things that clip on the headstock - I use one for my banjos and non-electric guitars.
If you are buying from a shop (which I'd recommend) ideally you should take someone with you who can play (in your case, if they aren't a leftie themselves) probably a right-handed version of whatever model of guitar you are thinking of, since if they can't get it to sound good then a complete beginner would probably struggle with it.