Can I buy parts from a salvage yard?
It is possible to piece it together but you'll spend a lot less time and money if you buy a whole car instead.
Some of the donor parts would be rather easy to get at a salvage yard but items like the main wiring harness are much harder to remove. It is quite common for salvage yards to cut wiring harnesses when removing other parts so there is a chance the harnesses you find could be damaged.
We've purchased donor cars for under $500. You could easily spend that amount just on the engine, transmission and subframe. Piecing it all together could end up costing you more in the long run than just buying a whole Cobalt.