I was recently e-mailed some questions by a someone who intends to take the New York exam this July. I figured I'd post some of my response for those in a similar situation who might have similar concerns. I hope it helps.
First thing I'd recommend is that you buy the NY Bar Bri Conviser. If you intend to take the Bar Bri course, then Conviser along with the rest of the set of NY books will be provided to you.
If you don't intend to take the course, the book can usually be found on Ebay or a similar site. Because you have a lot of time before the July exam, it may be to your advantage to buy the entire set of NY books. When it comes to memorizing outlines, though, go with Conviser for both the state portion and MBE. It really is a helpful book.
It is all a bit overwhelming, but just take it one subject at a time. Most people spend a few months studying, you have much more than that to learn the material. Once you feel comfortable with the content, start working out some problems. Do as many multiple choice questions as you can (again time is on your side here), and work through prior NY released essays. Memorization, and practice are the keys to doing well. It's a long, difficult process, but it gets easier as you move along.
As to your specific questions:
(1): Barbri is quite good for the state specific portion of the exam. I can't speak for the classes, because I didn't take them. I used Conviser to learn the state specific law, and the law tested on the MBE. I used PMBR to practice MBE multiple choice questions, but I've heard BarBri is a good value in that regard as well. Personally, because I was successful with it, I recommend self-study to others. But I know that some have been helped by the classes, so I assume it's a personal preference.
(2): I wouldn't worry too much about supplementing your knowledge. There is plenty to study in the review books. You really don't want to go off track by reading too many supplements. If anything, because you have so much time, you could read the the large Bar Bri books that come with the Conviser (if you take a course). The Conviser has everything you'll need, but those books will provide you with a bit more details which might help you to better understand the material you'll be required to memorize.
(3): The sooner you start studying, the better off you'll be. Before you start trying to apply the law to essays, and MC questions, you really need to gain a deep knowledge of the subjects tested. This takes time. A few months tends to be enough for many people, but if you have more that that, it'll really ease the pressure.
(4): The most important hint I can think of is to spend a lot of time reviewing the old bar exams released by the Board of Law Examiners. This won't teach you all the content you'll need (though it will teach you some), but it will provide you with the structure that the examiners are looking for when they grade the exam. It's really important to understand this prior to sitting for the test.