My issue with your question is not your weight. My issue is that you are questioning your ability to perform. Yes, the job is hard... but if you already think you might not be able to do it, you are setting yourself up for failure! Seems to me like you have an opportunity to help people and get a job but you don't really want it. I think this might be a better question for yourself. Get certified, build a resume, apply for a job, accept a position and work you butt off! The question of failure will not be your weight. If you want it bad enough, you will succeed.