same size 18s on all 4 w/sport package?

[steelertown]

I did some research and from what I understand, I can put 18s on a 370z with sport package if I understand right. My question is, well sort of a 2 parter. I would like to confirm that I could put 18s over the 2014 sport package without having to mod anything and for the part I am currently unclear on, can I put the same size 18s on all 4? Or would putting the same size on all 4s throw off the handling and make it unsafe? I don't track or race it I am asking for daily driver purposes and I just don't want to keep replacing 19s with how much they cost, but I don't want to do it if it compromises safety.

What size and offset would I be looking for? Sites like tirerack wont give you the option to search 18s for sport package.