Hello Nicole: I'm an RN originally from UK where I was faculty and now in USA for 15 years. I've practised and been faculty here too; also I taught for Kaplan, part time, for eight years.
Here are my thoughts: you seem to be an aware sort of student nurse with reasonable grades unwilling to spend about $400 on something you are not sure you need. A few years ago, Kaplan used to offer a complete content review type lecture format followed by a session of practice questions. Now the sessions are all based on practice questions, with the instructor using the questions as a basis to discuss strategies for approaching the questions and possibly going into some content with the more difficult questions. (Kaplan also offers a diagnostic test, lab situation and hundreds of questions to practice in your own time, plus content review texts.)
I believed the course, in any format, was invaluable to foreign nurses of any educational level because it helped with the approach to the multiple choice questions and the American way of nursing. I believed it was enormously helpful to students who had been unsuccessful in NCLEX. However, I'm not sure that a reasonably well prepared USA student needs it. I would suggest taking NCLEX-RN (CAT) after your own systemic preparation. In the event that you are unsuccessful, NCLEX will send you some feedback as to why this happened. Then you will have some basis for taking the Kaplan course.
During my faculty career (I'm back to bedside practice now) I saw class valedictorians fail NCLEX while many struggling students passed first time. There are many variables to taking NCLEX. All the old rules about enough preparation, sleep, eating sensibly, taking the breaks etc apply. Be systematic in your prep. Have a plan, review content. Do plenty of practice questions. Don't think too hard about the questions - this is entry level safe nursing practice. The test is not out to be sneaky or trip you up; it's a sound, validated format for letting you show that you are safe to be out there with patients. Don't be afraid of it.
I'm certainly not against Kaplan and believe they do offer reasonable value for money. You can easily spend as much on buying other prep systems which are not so comprehensive. Some of my former students who failed thought it was a great course (of course, the actual Kaplan teacher may make part of that difference!).
If you are looking for something simpler/less expensive, I do recommend a question book put out by the National Student Nurses Association. It always seemed to me to be a quality publication - some of the publishers' own books seemed to be too geared to the content of what they published.
I've very willing to help a student nurse facing NCLEX. PM me if you need more or a phone conversation. I wish you success. JNJ