Yeah, those things are in there good haha...I once broke a cheapo ratchet head taking that off when I first got my car. As long as you do it right...it'll be fine to drill out the broken bolt. You can try using an "easy out" to extract it.

Here's a couple sites tha may offer some tips:

http://www.brokentap.com/easy-outs.html

http://www.nichols.nu/tip009.htm

http://www.merkurencyclopedia.com/Me...t_removal.html

http://www.gis.net/~manjo/removing_b...tuds_bolts.htm