I've got some original tunes that I'm ready to put on CD and sell at my gigs. I see some on line services that advertise mastering service, usually around $30 per song. Here are my questions:

Is mastering worth it? Does it really affect the sound quality that much.
Is a mastering service woth it, or is there mastering software I can use at home with the same result.
What about mixing? Is there a service where I could send my Real Band tracks to be professionall mixed and mastered?

Brian