tx1hotshot

Ok guys,im gonna need a little help from all of you,please. Im thinking about buying a fairly new 350z convertable for my girlfriend,and I do not know anything about these cars at all. She likes them and they seem like a nice car. I would like to buy a newer car like a 2007 or 8 with low mileage. Is there anything I stay away from or look for that would sway me when making a decision? At what point mileage wise are there expensive repairs or PM work that will need to be done ? Also,I am 6.1 and weigh 275 pounds,I drive a 2002 SL500 Mercedes and its plenty big inside for me,but is this car large enough inside for me? I havent even sat in or driven one yet. All comments good or bad will be appreciated. Thanks