An instructor would probably benefit you quite a bit... But not in the same way it would benefit little Timmy that just got his first guitar for Christmas... Sometimes we all need an outside source to show us a few things and bring light to things that we've either been ignoring or haven't really noticed. That's what I love most about jamming with other people. It seems like everytime I jam with my friends or my friends' friends I come away with something... it may not be much but atleast I learn something. Where as if I stay at home by myself the progress is much slower and it may take me weeks to realize the same small thing...

Go in and tell the instructor exactly where you're at... Tell them that you're at an intermediate level but you would like to learn beyond that. They will most likely sit down and either play with you or watch you play some things to assess where they think you are... Then they can move on from there. Working on scales, chords, rhythm techniques, solo techniques... getting more into music theory and applying it to music... that sort of stuff. It sounds like you have the basic fundamentals down... which is good... as long as you've learned them right... If you haven't learned proper techniques, chances are the instructor is going to correct a lot of them. But you can expect to use the instructor on a very limited basis... Once a week to show you a few things and work on the things throughout the week... That sort of thing...

But yes, I believe an instructor could help you out quite a bit. Even if it's just to get your motor turning again.