You have two options for springs/coilovers...

Springs will bring you down 1.5" or so and are only about $200 for a new/nice set, while if you want coilovers (can drop you to the ground if you want, fully adjustable), rabbit made a kit to adopt VW coilovers onto the aveo, if you want "stance" then go that way, but it will cost you $500 or so. I would suggest the springs. There are a ton of threads with pictures so you can get a good idea of what you want.

17" are fine, 4x100 pattern, but if you drop it they may rub just a tad, you hsould be fine though, there are a ton of threads about tire/rim size and lowering options if you want to know more.