Slow down Adam. Take some deep breaths. FIrst off if you haven't shopped around yet do so. Find the best price for you and dont let the dealership push you around you have the right to walk out.
Secondly buy New I bought a 2008 GT, Sticker was $31600 I brought them down to $28200 before taxes and the BS. With a 2.9% interest rate and I'm only 20. Make sure the V6 is what you want. I started with a 2007 V6 Used base package and loved it but was still desiring the beefy V8 with all the pretty doodads :P. So i caved and traded in, on an Army pay check none the less :P
Next, The body kit. I agree with you the stallion is the most unique and awesome body kits out there but....
It needs to be painted. $799 + $500-$1000 then it needs to be installed and I am not to sure on how much that is.
Moving on to exhaust, the best id say for the V6 is the Flowmaster 40 you can even have a shop cut you some custom pipe and mount two up there. They sound great on idle and give your GF some fun in the seat next to you, but when you stomp the gas you still feel something missing.
It is all up to you. Trust me V6 owners im not busting on you guys at all I love the new 4.0 but I got the V8 flu and cant shake it

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All I can really say is take your time. Do not rush things especially if its your first purchase of a vehicle. If you look at it..save the money you were gonna toss into the body kit and exhaust and put it into a V8.