Just finished doing the same thing - for the first time. It wasn't all that bad - but was a lot of work.
Make sure you know which direction the underground drain from the present toilet runs. Nothing more frustrating that cutting a hole and not finding the sewer line.
Plan on lots of dust from scoring the present concrete - and smell to permeate the house for a day or so --
I'm sure you'll get more advice from other "more qualified" people on this site... they've been invaluable to me.