My radiator has some fins that aren’t totally straight, is that ok?

Yes. While damaged or misshapen fins aren’t necessarily the most aesthetically pleasing, a few here and there will have an immeasurably small impact on performance. Individual fins losing a portion of their efficiency in an array of hundreds to thousands of fins won’t end up noticeable. They can also often be straightened out with a small flathead screwdriver or other small flat metal tool.