The major difference between the I30 and the I35 is the engine. The I30 had a 3.0L engine, while the I35 got a more robust 3.5L V6. The engine made 255 horsepower.
Styling was also changed when the name was changed. Other changes included larger brakes and a better suspension system. They wanted buyers to see the car as a sports car in a luxury sedan body, but for the most part that did not convince anyone. Some more upgrades were offered than in the previous generation, but this car was still seen as entry-level luxury, which tends to be a poor class to be in for overall sales and profit alike.
These cars can be found on the used car market. Check the classified in your local newspaper. If none are there, my second resort is usually eBay. There will be some listings there, I can almost guarantee that. There will also be parts, including rims for anyone looking to "trick one out."