Im getting into this ska band (Agent 84)and they needed some1 to play trombone and I said yes, and now im not sure which kind i need

You can play any kind of t-bone that you want in a ska band. Try out a ton of different ones and pick the one that you like best. You probably want one that is bright sounding and kind of harsh almost. An F attachment is nice but not a necessity. Good luck! ska bands rock!