I'm assuming you would be willing to live with cosmetic issues such as rusting body panels. If so, I recommend that you ask your shop to do an evaluation of rust on the entire vehicle. What you want them to be primarily looking for are potential future structural issues, which would require costly repair. You're basically trying to find out approximately how much longer your Aveo can hold out before rust overtakes it. That inspection shouldn't take long, or cost much $$. They should be able to give you a good summary fairly quickly.