the part that attaches directly to the motor is call the header
you should not have removed it because now you'll have to clean and prep that area of the motor, replace the gasket and in the mean time you risk damanging the internal parts to your engine (since it's pretty much a window directly into your valve train and possible the combustion chamber)
when I was working on my motor I place masking tape over these holes for this very reason.
it probably doesn't attach with studs.. most likely just bolts
however pieces down stream from that DO likely attach with studs where two pieces of pipe connect together.
every exhaust is slightly different and me not knowing much about the Grand Am I can't comment on what what they placed after the header.
you can weld it together if you like, since you have both pieces, you tell me does it look like it was a flanged connector that separated or was it a length of pipe that snapped in half?
you might not even be able to weld it if the metal is too weak, in which case that section would have to be rebuilt using new pipe.
ether way it needs to be done (or at least started) ON the car to ensure that the alignment is correct.
EDIT:
this might help you determine what part actually broke
http://newgmparts.com/partlocator/index.cf...playCatalogid=0This post has been edited by twistedsymphony: Jun 23 2009, 07:06 PM