A basic problem I've had in the past too. Personally, I would recommend getting a consultation from a specialist. They could easily repair it if there is not a big deal there. But, the issues aren't repairable; this site will help you get a new horn
https://hornblasters.com. They have a fast shipping. I remember wanting to replace it myself; now I know it was stupid. Without experience and knowledge, it is ridiculous to even try. Stop it; get some help! A professional can do the work for you. While watching him, you can learn how to do it yourself. As a beginner, it is a cool experience.