I use midi guitar all the time..
You need a 13pin system in your guitar and an interface to convert audio (signals) to midi (numbers).
I'd suggest looking into an Axon AX50
http://www.axon-technologies.net/module ... 6&menu=102 as interface, as you get more control with the Axon than with the Roland GI20 (those are the two most accesible options today)
http://www.roland.com/products/en/GI-20/ . The Axon track's a little better ión the lower strings, especially when you set it up properly in the software editor. These interfaces have no built in sounds, but tracking issues are very few in todays boxes. You can even shred and get really good tracking ('tracking' is how the notes played on your guitar translates to midi).
I also use a Roland GR20 synth with built in sounds, which I love for it's playability
http://www.roland.com/products/en/GR-20/ . It actually tracks pretty well (so it IS possible to use this as a guitar/midi interface to track your Vi's), but the big advantage is to record it as audio, so you don't strain your computer. I sometimes run it through my tube guitar amp and record with two mic's. It's amazing what that can do in terms of realism on strings, brass and synth patches.
You can get actual synth ready guitars like Fender Roland Ready
http://www.fender.com/products/search.p ... 0144660306 and several of Godin's. I have a Godin freeway SA
http://www.godinguitars.com/godinfreewaysap.htm . More brands are putting synth access in their guitars now, and high end brand Parker also have one. You can also just get a Ghost system and install it yourself in your favourite guitar, or have your luthier do it
http://www.thomann.de/gb/graph_tech_gho ... kit_st.htm .
There's a script for the Native Instrument sampler Kontakt (for v3 and v4), called Gtak
http://evenharmonic.com/products/gtak which allows you to play it as a multi, meaning you just play the samples in Kontakt like on a keyboard. I use that all the time, works like a breeze. But midi guitar works nicely for any Vi.
There are of course things that's not so easy to play on guitar, if you are to play it for realism, so it won't completely replace a keyboard or piano, but it's so much fun and your creativity will benefit from the boost it gives you, when you hear that Urdu flute sweep across your fretboard

Here's a fun vid
http://www.youtube.com/watch?v=tben3v6Y ... re=related
I have yet to explore it to it's limits, but it's just a whole new world opening up for you, when guitar is your main instrument. Often guitarist's feel the urge to play long solo's, and that's great, but it's often on music that doesn't HAVE guitar solos

Midi guitar let's you keep feeling you are playing guitar, even if you haven't recorded an actual guitar solo for months.
I can highly reccomend it, Jen!