Mine was 16 weeks but that included a lot of class time and I was a brand new nurse working in a fairly critical ICU. You should be okay but if you aren't ready when the orientation is up, let your manager know. Most places are good about giving you more time if you feel you need it. No place wants to set you up for failure!! Good luck if you take the job:)
I would think maybe this would be good for a quick fix, but I wouldn't recommend leaving it in there for more than a short period or it could irritate the inside of their rectum and start to break down the surrounding tissue. Even though the balloons on the rectal tubes look big they are specifically made to sit properly and not cause breakdown on the inside.