Its very common, almost guaranteed. As far as I know, the front-most bolt is the one that breaks most often (I may be wrong). I had a local garage that I trust do the work ( I didn't feel like dicking with it, extracting a broken bolt is enough of a PITA, without worrying about screwing up block threads). They replaced the bolt with a heavier grade unit that should resist the expansion/contraction of the manifold (the common cause of this). The dealer is going to charge more everytime- IMO every gearhead, no matter how mechanically inclined, should have a trusted local garage for the stuff they can't, or just don't feel like doing. Be sure to closely examine the manifold itself for cracks as well.