stupid emissions testings..... your going to want to have the cat. and muffler in place.
the cat. should come off fairly easily. few bolts after the exhaust headers and a few more to disconnect the pipe from behind the cat.
unclip any o2 sensors in the way of removal and re-install. blast all your bolts with some kind of anti-seize lubricant such as pb blaster a day before or two, and if you have any gaskets in the exhaust line, replace those too.
Previous owners may have not used replacement gaskets if they worked on it and had not brought it to a garage for the job to be done.