I have recorded many vocals and other tracks (including acoustic guitar) using Realband. It is a very capable tool.
For your guitar.. it sounds like you need a mic and preamp if its an acoustic.. what have you got to work with?
Give us soundcard info and any other equipment you have, then we can can make an econimcal suggestion..
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I do not work here, but the benefits are still awesome
Make your sound your own!