/ic/ - Artwork/Critique

How good do I need to be to draw a graphic novel? I've seen some that managed to get published even though the art is pretty bad. I'm not that great myself, and I only really draw occasionally as a hobby, but I've got a movie screenplay I've been working on for while I want to try and illustrate it. Ideally, I'd like to end up trying to sell some copies, but even if I just kept it to myself or put it up as a webcomic or something, I think it could be good practice and get me drawing more.

Pic related is a scribbly sketch I made a long time ago. I don't really have anything too finished.

I wrote a screenplay that has no chance of actually being bought/made into a real movie. Should I adapt it into a graphic novel and draw it myself? I haven't done anything but little doodles in 3-4 years. I'm probably not even good enough.