I need some theatre advice.. (TW for panic attacks/anxiety attacks)

So I plan on being in theater this year at my school, I want to be on stage but I am worried that I will end up having a panic attack because of me having really bad stage-fright. I do not want to embarrass myself nor mess up the musical. The biggest role I put myself for it Nicey-Nicey Johnson. I do not know if I am a good dancer and same for singing so I am probably not going to get the part( Since he is a side character I will be doing some singing and idk about dancing but I would think so). The try-outs are Monday and Tuesday and I am really nervous and IDK what to do.. I do not know if I should study one of his parts in a song or not, I really wanna push myself but I know if I do lead then I am pushing too far but I am worrying side character would be too much too but I'd prefer not to be a background character nor backstage. What should I do?

.P.S. The musical we are doing is "Guys and Dolls".