Exhaust replacements can range from very easy to very difficult, depending on what needs to be replaced. This could range from the pipe past the muffler (being the easiest) to a full replacement from headers back (most difficult and most expensive on parts.) A typical replacement will be 'cat-back' which is from just behind the catalytic converter (often the most expensive component) to the end.
In an ideal world, you can simply unbolt the exhaust hangers, pull the pipes apart for the areas you need to change, and put the new pieces in. But of course exhaust systems rust, bolts rot out, and pieces fuse together. Iv had clean muffler replacements take 10 minutes, and other jobs require torches, cutoff tools, and angle grinders and take hours.
I would start by getting under the vehicle and checking what parts need to be replaced, and see if they will be easy to take apart from the bolts. If not, I would recommend going to a muffler shop to save yourself the trouble. They tend to be very quick and inexpensive. Iv even had a replacement of a full system on a Camaro (parts and labor) at a muffler shop cost less than just the parts would have if I had done it myself!!
If you are lifting you car to get under it, don't forget to use jack stands!