Ask one of our sponsor dealers....
Depends ENTIRELY on the dealer. Basically, think about it like going to shop for a new refrigerator or other big appliance:
You talk about what YOU want, the dealer shows you stuff or a car on the lot if they have one close, you go over options and "build" what kind of car you want. They either have it, can locate it, or they can order it.
I've found it 1000% easier by securing any financing in advance. There's nothing wrong with the dealer doing it, but more often than not, shady types ask you what you want to pay per month, then adjust the interest rate to fit that payment. Watch out! Do your financial homework first as to your budget. Unless you really want it, avoid any of the dealer "add on" crap that does nothing more than line their pockets. Any "mandatory" add ons they may claim because they're already printed on the invoice form aren't really mandatory either. If you don't want them, they can't make you pay for them. IF they insist, then get up and walk out. Dealers have more psychological tools in their arsenal, and remember, when it comes to brass tacks, they're NOT always in your corner (not all...sponsor dealers here are some of the best)
If you're going to buy a new Camaro, talk to your local insurance companies first, to get an idea what you'll be paying for that. Also any local taxes you'll be liable for. That all gets included in the price.
I can personally attest that Eric at Classic is awesome to deal with and went out of his way to make our buying experience a 100% positive one (which is rare nowadays). And just read about the other sponsor dealers here. Quite a bit of the same.
You're in Illinois, so I wouldn't hesitate to contact Camaro Scotty since he's kinda close in Wisconson or Anna at Sparta Chevy. Regardless, start talking to some dealers once you're sure of what you want.