Steve:

Pull the bumper.

Two big bolts and some plastic push pins and maybe.. a phillips headed screw or two on the wheel wells. Can pull the one on an E30 or E39 in 30 minutes max.

Bonus = clean all the leaves out by bottom front radiator core support.

You can do it!

I just use a small pair of diagonal cutters to work those clamps. I know there are several companies that make a specific tool for those clamps. As Jase said, it may be easier to pull the bumper to give you more room to work. The ones that come to mind are Hazet 798-2 and 798-3.