Your girlfriend has good taste
The auto will of course be a little lower on the power but it will be easier for her to learn. You can always add 2" sports exhaust and extractors
which helps heaps, add a snorkel for better air induction..... maybe even a supercharger later on
Re warrantee, it depends on the dealer really, when I had my 2" lift and 215's - it was understood that anything relating to what I had replaced was not covered by warrantee. (shocks / springs etc) but all else was cool. I bought mine off Action Suzuki in Parramatta and they were pretty happy to look after me.
Its only when I started playing with a bigger lift and tyres (the castor bushes changing angles and things) they got a bit "hmmmmmm" about it.
I have a rockhopper now - but my warrantee has run out anyway!
Can highly recommend Gosford Suzuki for buying a Jimny too, they will really look after you.
Don't forget to put on recovery points - I think Big Balls Offroad may have some left, if not GRP over at Moorebank have them in stock - on it BEFORE you go offroad. *****Do NOT Use the existing ones, they can be lethal if they tear off******They are only tiedown points!!!
You can also put on a bull bar and towbar later to use as well.