The courses are designed only to teach one to pass the test. They teach nothing you shouldn't already know before you begin. It is much like a driver's license exam, with questions worded as though to confuse you, which is why taking the course is helpful.
The written exams are multiple choice and therefor the correct answer should be (but not always; I was told to choose the closest to correct in this case??) right there in front of you. If you plan to make a profession out of this, beyond US territorial waters, you'd be a lot better served to go through the RYA system as the US small craft (under 1600 grt) tickets are worthless and unrecognized by any authority other than the USCG.
I have yet to have an insurance company discount me for any of my licenses or experience, by the way.
You may also need a TWIC card (I don't know if it's required for OUPV, but it is for any larger ticket, as is an FCC marine radio operator permit).
Anything you need to know is available at;NMC Charter Boat Captain Page