Ok lots of questions here, so I'll try to attack them one at a time.
You're not sure if you want to lower it - absolutely do not get a kit and spoiler then b/c it will look very bad with a huge wheel gap. Eibach pro-kits will only lower your car around 1.5" for a nice look.
If it snow a lot in the winter, I would seriously think about not getting a kit, or get a second car to drive. If you do get a kit, I would get adjustable coilovers to go with it so you can raise your car up in the winter. Apex'i makes the WS coilovers, which are pretty cheap (for true coilovers), but perform well.
As for the kit material, I think urethane is the way to go, but I honestly don't know too much about them. You'd get it painted at a local body shop. It could cost 300-500 to paint it I'd guess.
As for rims...
www.tirerack.com www.wheelmax.com www.discounttiredirect.com and there are many more. You could search around the forum for suggestions.