To check if your course is valid contact Oracle University. They are the only people that can give you a definitive answer. My guess is that if it was not actually and Oracle University course it won't count, but check to make sure. You can get contact details from here:
The OCP program has a specific syllabus and the OCP guides are designed to cover that syllabus. No more, no less. If something only warrants one sentence in the exam it will only get one sentence in the guide, even if in reality that topic is large and complex. Passing the OCP does not guarantee your ability, but it shows a certain level of understanding and it will help you to direct your learning efforts.
The length of time is very personnal. I don't think I've ever taken more than 2 weeks to complete a certification, but I've heard of people taking 4 months of full time work to do it. I've got alot of experience so revising for me is just a case of brushing up, not learning from scratch. I also use this stuff all day every day, so it is engraved on my mind. I guess this makes me one end of the spectrum. On the other end are people with limited Oracle experience who don't use it as a job. These people are likely to take longer. I think the sensible thing to do is just approach the first exam and use this as a barometer. If you feel ready quickly and pass comfortably then you will have an indication of the timescale and level of effort involved. If you fail you know you need to put in more effort.