Save your money on books or magazines. It's simple, similar to stretching sprue-use a candle. Hold the part over a lighted candle-not immediately over the flame, but high enough to warm the plastic. It will soften. When it does, you can use an object like a pencil or a dowel to shape the fender. Once you have it bent to the general shape you want, let it cool, and then you can refine it by thinning edges, adding nicks, etc.
It worked for Shep Paine, it works for me.