Don't do it, I say it being a body kit owner myself even.
Here's my reasons.
Ricer Mentality - Even if you do it because you think it looks good, other people will look at you and label you ricer.
Expensive - It's almost $2k in the end to have it fabricated to fit your car, plus painting it (a must). Don't cheap out if you spend the money, there's too many body kits on the road that half fit and weren't done right that look hideous.
Constant Reinvestment - Like many people here said, a curb check once, some roadkill, a speed-bump. All of these can easily cause about $500 in damage minimum with a body kit. (New front end, repainted, etc.)
Attention Getter - Neons, Vinyls, Body Kits, they all draw attention to you and your car. You will be followed everywhere by the police. I'm followed home nightly taking the same route night after night by the cops. Also at every stoplight some doofus is going to try to race you, or rev their engine. It gets annoying.
Also a Maxima body kit sounds like ass for the record.
My advice is the same as others, really think it though and if you do it then do it cleanly and do it right the first time. Also forget performance if you're going to kit your car. Adding a few hundred pounds of fiberglass isn't going to make it faster.