Well you might still be able to do it. Most of the graphic work is done on the PC with things like Photoshop in which you can go back or undo the previous step in case you do make a mistake. As such you may be able to do some minor graphical work.
I can tell you from personal experience, my hand is not the steadiest thing in the world. I have messed up working on images more times that i can even count. I just undo what i did and try again. Yeah it may take me more time, but in the end i still end up with the image i want and it feels great to have done it myself.
The best thing that can be said, get something like GIMP or Paint.NET and try. There are tutorials all over the net for these applications and at worst you find out that you cant do it or dont have the patience for it. The flip side is you may find that you can do it and actually enjoy it.
Like i said it may take more time to get the same thing done as someone with a more steady hand, but it isnt impossible. If it doesnt work, at least you can say you tried.