Just sing along to your favorite CD's and memorize the lyrics. Tape record yourself singing and get opinions from your friends. Sing from your stomach and not your throat. No vocal coach required.
Real vocal coaches, from what I understand, are worth their weight in gravy. But a software? I'm not familiar with it. Do what I did, just start singing and keep going, no matter how many times your bandmates try to replace you.
Get some suckers to program you some software. Promise then lots of Mountain Dew and sexy hotties. Trust me, they'll bite. #lolprogrammerslol
Be bad. Get bitches.