It depends entirely on how you do the course. Most places will offer a course when they need new lifeguards, so you could enqure at the pool that the course is at. If that fails, then getting a job will depend on how employable you are, e.g. if you only have the NPLQ (so no other qualifications/experience), then it will be quite a bit more difficult, if you can do other roles in the same center (bar/cooking, if they are in-house, first aid is always good), then they will be more likely to hire you. Also, experience in areas of responsibiliy/experience cleaning/safety is useful.
As for the course itself, I didn't find it that hard, but, having said that, I have had to watch people do a course this week, and they truly were appaling (timed swims were 1.25 after 5 days, supposed to be 65 secs).
The most difficuilt requrements of the course are the timed swims, deep water rescue, and the tows.
Post more here if you want some more information.