1st Interview you will meet with a Talent Acquisition Manager. You will basically review your resume and they may ask you about specifics of certain jobs you had held in the past. I was offered a second interview right on the spot.
2nd Interview- You will meet with a Area Manager and a Branch Manager at the possible site you will be working out. This process usually last about two hours. The first hour you can observe and make sure to ask a lot of questions. Many of the employees went through the same process that you are currently going through. The second hour of the interview will be the time where they really drill you about your resume. They will ask you for specific situations.
I would not say the interview is very difficult, but it is not easy either. They really want to make sure you can handle the difficulty of the sales position.
In the end I did not pursue a 3rd interview because the job did not align with my interests, but I have heard that the 3rd interview is with a regional VP and this is the time where they do background checks and try to learn more about your personality.