I also saw that documentary and having worked on ships, on Royal Caribbean it made me very angry. It was very one sided and misleading. Yes you work long hours, but not as bad as the programme made out. A normal day is 10 hours, split over the whole day (so maybe some hours in the morning then a break in the afternoon to get off in port and then a few more hours in the evening). You will have to do some training in the first 2 weeks onboard and some of it will probably be in your own time but you need to know the safety stuff and you will still have time for yourself. Your salary will be mostly salaried with few tips so less chance of it being wrong but just double check your contract when you get onboard. In terms of the housekeeping staff paying people to help them, that is their choice and fairly rare, and the housekeepers were getting paid well with tips, i did the processing of salaries every fortnight and they were on a lot more than me!
Please dont worry too much about what you've let yourself in for, be prepared for long hours and being tired but the ship you are going to looks amazing and you will meet great people. The programme didnt show the social side and there is definitely a great social side! Ship life isnt for everyone so you might like it, you might hate it but whatever happens, forget that programme and go with an open mind, at least you have tried and it will be an experience you will never forget! Good luck :-)