first off i dont think i told you welcome yet.....so
..lol
secondly....it all depends on what direction youre going with your modding e.g. power/performance, looks/cosmetics, or (my personal favorite) all of the above...and from what it sounds like in your post...youre going for both...
for the rims....a relatively easy/cost effective upgrade is the SS/SC or SS/TC rims (both are 17s)...
i cant give a good answer for the muffler because it depends on the tone/loudness/etc youre going for...some sound great...some sound like a$$...lol...
for basic modding...
power/performance...most people start with intake, header, exhaust, lowering....and go from there..
visual/cosmetic....debadging, tint, tinting tailights, HIDs, lowering etc ...
hope it helps...