Read the installation instructions carefully. Particularly the notice to NOT leave a key in the lock when you do the installation. If you have a key in the lock while you install it, at least for me, it seemed to make the lock work funny and jam. Solution - take apart and reinstall with no key in the lock. Then it worked fine,
I was concerned when I opened the box that the existing hole in my door wasn't big enough to accommodate the complete lock with mounting ring included. But in the instructions it said how to remove some of the mounting ring so it would fit my inch and a half diameter existing hole.
A pro would likely be able to swap an old lock for a new one in 5 minutes. It took me about an hour to do two doors, including removing the old locks. But I've got a great understanding of how it all fits together now. The locks I replaced where Schlage locks that were maybe 30 years old at least. These new ones are so much easier to install then if I had to put the old ones back in. I'm glad I bought new locks instead of just getting the old locks rekeyed.