You want to keep the overall wheel/tire diameter the same. So if you end up getting bigger rims, you should put on lower profile tires. Deviations in the overall rim/tire diameter will result in speedometer inaccuracy.
The 7th gen civic has a wide variety of parts that are interchangeable. Not as much as the 6th gens, but there are still plenty. Tons of side skirts, tons of front lips.
Here's a listing of body kits from one seller for 2001-2003 civics -
http://www.andysautosport.com/honda/2001_2003_civic/exterior/body_kits/
There are many more.
For front lips, the big ones are Mugen (style), Type R (style), and the factory aero lip kit.