Would long distance running affect my sprinting?
You have two different types of muscle fibers – fast-twitch and slow-twitch. Sprinting is done by the fast-twitch, and distance running is done by the slow-twitch. You can be strong in both, but to be competitive you need to focus on one. Speed work (400m repeats) are great for distance runners, but I don’t think distance work is what you want for sprinting speed. It won’t “hurt” you, per-se, but it won’t be the best use of your training time, and you could injure yourself over “the long run”.
