Wow what a great purchase you made! I don't always prewash before quilting but I do test for color running. Especially a red color. I cut a small 2"X2" piece and soak it in a cup of boiling water to see if the color is going to run.
You should also check out the Quiltville.com site. Her scrappy quilts are great. I have made a few and they are a great way to use those strips you have that are already cut.