I am looking for a simple way to get reverb from audacity - similar to a guitar amp that just has a knob from 1 to 10. Is GVerb the correct effect to use for this? It looks too complicated and sounds horrible - even after fooling around with it. How can I get good, easy-to-use reverb with Audacity, since I won't be recording with any reverb?
There are a few pretty simple LADSPA reverb plugins that will work with Audacity. Start looking at Steve Harris' docs page.
I like the Plate Reverb he lists for vocals and general reverbiness, but if you are interested in a guitar reverb you want a "spring reverb" sound.
The LADSPA Impulse Convolver has what appear to be compiled-in presets for about 20 different guitar amp spring reverb units; I haven't used it, but impulse convolution is a good (if computationally expensive) way to do reverb and if it does what it says on the tin you should find one of those sounds that work for you.
I'm not sure if you already knew this, but the best way to use GVerb is to duplicate the track you want reverb on and then apply GVerb to one of them. Then you can adjust the level of reverb in the mix.
See: Audacity Wiki