It's possible that you have rust on the bearings, but you may not. Based on the gummed up carb, it sounds like you were using fuel with castor based oil, which is actually a good thing. I had a bunch of engines that weren't used while I was out of the hobby. Out of all of them, the only one that had rust inside was the one that was run with synthetic lube fuel. The ones with castor were all fine.

Use alcohol to clean out the inside of the engine. Pour some down the carb and in the exhaust outlet. Turn the shaft back and forth a bit and then pour it out into a clean bowl. The color of the alcohol will give you a clue if you have rust or not. Once the alcohol is coming out clean, and before you lube it up, note how it feels when you turn the shaft. If you feel the slightest bit of roughness or grinding when you turn the shaft, it would be worth inspecting/replacing the bearings. A new set typically runs about $20-30, cheaper than a new engine.

Bearing replacement isn't too hard, but if you've never done it before, there's the potential for reassembling the engine wrong. See what you're up against before deciding what you need to do.