Doh! Broken screw holding coil in!

[amg kodiak]

Argh...

Okay, so I was changing the plugs on my C36 this afternoon and all was going well until I got to the number 6 plug. The 6 plug in my car is beneath the #3 coil, thus the coil must be removed before you can access the plug. There is a small flathead screw that holds the coils in place. As I started to loosed the screw, the head srtripped!! and not a little strip, so that using a different bit would possibly allow me to remove it. The screw head broke where the notch meets the screw body- only leaving half the head!!.

So two things:

1) How do I get this damn thing out so that I can replace the #6 plug?

2) Is my car going to be damaged by running 1 OE bosch plug and 5 platinum 2 bosch plugs? I cannot imagine it would be a issue in the short term <100 miles, but better safe than sorry.

~dnm