Having a proficient guitarist contribute to your song is a good idea and all, but such suggestions don't address the original post. Toddskins is looking for someone to polish HIS tracks, his MIDI.
Unfortunately, for that to be a viable option anyone looking to fix up your track would need to also own the same instrument. Every sampled guitar has a different set of implemented articulations, and each uses its own keyswitched or velocity-dependent articulation selection scheme.
Q: are you a proficient keyboard player?
If so, it's just a matter of practice (OK, a
lot of practice) to develop playing techniques that translate to a credible faux-guitar (or any other instrument) performance. (Hint: your pitch bender is your best friend.)
If you are not a keyboardist, start by learning every capability your sample library offers. Then experiment with switching articulations and hand-editing velocities in the PRV (a guitarist never hits every note with the same force). Listen closely to the vendor's demo tracks, as they will give you an idea of what the library is capable of.
In either case, several vendors offer sample MIDI tracks for download, which is great because you can see exactly how they got their results (almost always far superior to your own first attempts!). Orange Tree and Indiginus both include some sample MIDI in the install (look in the Demo Song subdirectory for OTS, or the Demo Materials / MIDI demo subfolders for Indiginus).