Should I change my cover letter? I think I'm GURANTEED a job if I change it?

Um, if you were applying to sit on the board of a charity, that might work. But even then probably not. My family runs a few fairly large charitable organizations and if we got a letter like that, I doubt we'd hire you. I'd honestly wonder about both your sincerity and your ability to cope with normal social situations. And if you're applying for any secular job, that's an automatic no. You won't even get an interview. Cover letters should say why you're interested in the particular job, what strengths you can bring to the job and that's it. And you shouldn't be using the same cover letter for every job you apply for.