Catbacks bolt right up, thats why they are so great! The only problem you'll run in to is your old bolts will be rusty as ****!
True depending on year and location of the car.......its a breeze.
I did my friends Sentra SE-R in about 7min with a friend (yes i timed myself:fawk: ) Its a 03 so the bolts didnt even have a water spot on them. I used jackstands........and thats it.:thumbup: