Hi,
1.) In regards to Quant:
If you find that you experience serious difficulties, you may want to supplement your current regime with independent study of key concepts. No program teaches math from scratch; it would take about 6 months to a year of just math studies. Also, remember that part of achieving success on this exam has to do with strengthening your weaknesses AND your strengths. The section you are strong at will help you with your overall score, too. Remember that you will need to learn how to attack the GMAT Quant via various techniques aimed at saving time, and NOT solving everything fully. You can certainly do a bit of work on the side in math to strengthen your skills, as this cannot hurt.
2.) In regards to Verbal:
If you feel you need more grammar practice I would recommend "English Grammar in Use" (intermediate and advanced levels).
Please be aware that almost all grammar books tend to be exercise-oriented and often go into much more detail than what the GMAT tests. In addition, many grammar books do not deal with certain sentence structure issues (e.g. dangling modifiers). You need to look for something that can help in that regard too, or simply fill that gap with a proper course. You need to cross-reference what is on the GMAT with the book you get, but "Grammar in Use" is probably the best grammar self-study book available.
Please remember that in order to beat the Sentence Correction section, you need to know the grammar and the techniques, AND how such grammar is applied in the GMAT itself.
3.) Specifically in regards to the IR section:
The changes to the new GMAT are relatively minor. The new GMAT replaced one of the two essays from the AWA with a new integrated reasoning section. 90% of what you will have already learned will be valid for the new section. You will only need to spend a few more hours to learn the new Integrated Reasoning section. It is a short section, not even as close in time and effort as the verbal or quant require.
According to mba.com (you can also watch some videos on the IR section and get additional info here) the Integrated Reasoning section consists of one 30-minute section, made up of 12 questions stemming from 4 question types. A prompt or question type might have multiple questions that go with it. There may also be a necessity for switching between ’tabs’ within a question prompt/type. Basically these new question types are graphic in nature and require, for the most part, an ability to analyze data (words, charts, graphs, etc) in order to come up with key insights that require math skills and verbal skills.
The IR section in the exam is not part of the 200-800 score and is non-adaptive. It is graded separately on a scale of 1 to 8. More importantly, it is very possible that many schools will not look at that section as important for now, as it will probably take them some time to determine what an appropriate score is for their particular programs. However, please check with the school programs you are applying to. Most schools have not posted how much they wish to see on the IR section because this does not seem to be a concern for now. Do check though.
Your job is to try to do the best you can there but the concentration should still be on the Verbal and Quant sections. The good news is that you do not need much new raw knowledge but rather you need to become familiar with the question types and practice a bit there so there are no surprises. This section has more of a 'wow' factor as it is graphic and the questions are very different than what has come before so this is what scares people but it shouldn't because of the reasons outlined above.
You will not need to deal with IR until later in your GMAT studies. In fact, you should only be studying for the IR section more towards the end of having studied everything else, because it requires much less studying time, and you will learn most of the skills necessary beforehand.
In all, you do not need to worry too much about the IR. It is not where you should concentrate your energies. You still need that score out of 800 as that is still the measure for almost all schools.
Sincerely,
Evan