headers should take you a couple of hours.. not to bad.. general wrenching.
cat back takes about an hour or 2. you will need to line everything up, and make sure it tucks up nice and neat. so as not to touch any part of the body, or supports..
on a scale of 1-10. 1 being super easy, and 10 being take it to a certified mechanic..
I give it a 3.