Taking the bumper off is a simple job, just lost of nuts / screws to take out. Is the toe bar original Audi, I assume not as you would have discovered it's a piece of pi$$ to take off by now. If it's an after market job then it's an unknown task and you're just going to have to get on with it. Get some blanking gromets to infil the bolt holes once removed, a bit of grease on them wouldn'y go a mis to prevent rust, or paint them (the edges of the holes) before fitting the gromets.