Recording near studio grade guitar tracks?

Does anyone have any suggestions on how to record clear, studio grade guitar tracks in Garageband 11 using their interface (their pedals and amps). I'm having a hard time trying to create a sound that doesn't sound too echoey or too confined (sound too muffled and bassy). I'm also having trouble with too much feedback (humming and whistling sound) when not playing and having to push up the Noise gate level so that the sustain notes are cut off. The guitar tracks tend to be messy and unclear. This sorta goes with vocals too. I'm fairly new with recording with such a complicated interface (I had an 8-track digital recorder) It's kind of driving me insane.