Yeah. It will.
If you don't plan on trying to get everything you can out of the car as far as MPG goes then you won't realy notice it. If you want to get the most MPG then it will limit you in the long run.
Here are pictures of someone that has the full body kit as well as different wheels.
http://www.cleanmpg.com/forums/showthread.php?t=1400
When he tries he can still do great with the FE.
I think the amount of air in your tires might be more important than the added weight.
Just remember though that what ever mpg you get with the mods, it would probably be slightly better without them.