Someone have some pictures or instructions I don't have much experience with shaping/cutting plastic without a trace line so I could use some help?

 

use some tape as an outline of where you want it to be cut then just use a cutoff wheel or something to cut through it try to stay back from the tape when cutting so you dont mess up it doesnt have to be perfect you can smooth out after rough cut, then after that you can sand the edges up smooth so its right on the tape and will have a nice clean look if you know what i mean, that blue masking tape works good for this. some1 might have a better way but this is a pretty good way in my opinion.

 

Using tape is a great idea, some just go at it with a sawzall, and eyeball it. If you have any spare cash, maybe look on eBay and get some race cut fenders,and save yours. Like 91 Warrior said, lay out some tape, stand back and look at it and see if it looks like a good line, then cut CAREFULLY !! best may be to cut it 1/16" wider, and then sand or reshape to get a smooth line and best look.