Well, since this is the first time that I've stumbled on the forums, and you asked a question that I can answer, I'll give it a shot.
I owned a 01 Sunfire, mechanically exactly the same as the Cavi, so I remember much of what is needed.
Let me just get this out of the way right now, if you have not joined Jbody.org
, I would recommend you do that soon, they have lots of knowlege there for you to use.
Now, to answer your question, there are a two ways you can lower your car.
1. Lowering Springs
2. Coil-over Kit
The first thing you need to know is that if you're going to be lowering the car, you're going to need to change your shocks, thats first and foremost the most important thing you need to do. Not only do the stock shocks not take to kindly to being lowered, but you'll get much better performance out of an aftermarket shock. Koni
has great shocks that are used very often with jbodies.
Lowering springs will lower your car a certian ammount, around 1.5" or so. They are much cheaper than a full coil-over system, but they also do not allow any sort of change in ride height, so you're stuck lowered X inches.
Coil-Over kits especially Ground Control
and Koni dampers are a tried and true method for custom ride height coil-overs for a J like yours.
Now, you can run lowering springs on your shock dampers, but you'll eventually blow them, and have to replace them anyways. Expect to pay anywhere from between $600-$1000 for replacing springs and dampers (lowering springs themselves will only cost you about $200)
Hope that answered your question, and really check out J-body.org
, they helped me out a lot when I first started out and I learned a lot.