It's pretty straight forward to replace "IF" you have the right tools. The mount is located in the transmission tunnel right above the cat. The cat has to be unbolted to get to the mount.
If you live in a area where they use salt on the roads more than likely you will catch hell getting the bolts free. That's where the 1/2 breaker bar, Pb blaster come in. If that doesn't work you can use a propane torch or a cut off tool. If you have to cut it off those bolts will need to be replaced so if this is your only means of transportation keep that in mind.
The other thin would be getting the car high enough off the ground to have room to work.
Floor jack, 2 pair of ramps/jack stands. you will need all four wheels off the ground for this.