Yes, this is all rather new and subject to change. That said, some tips:
1. There is a sample test. You can find it at the faa.gov site. I uploaded the copy that was current as of July 5, 2016.
2. After each question on the sample test there is a code. For example for Q1 the code is
PLT064 / UA.V.B.K6a and this gives you a clue as to what might be tested. The PLT codes refer to the Learning Statement Reference Guide. I have uploaded a copy of that Guide and highlighted those codes which are on the practice test.
3. The second part of the code (e.g., UA.V.B.K6a) refers to a section of Airman Certification Standards. I have uploaded that for you. In this case you would find task V.B.K6a on page 13, which tells you that Aeronautical Charts are being tested, and you are referred to AC 107; FAA-H-8083-25; AIM which would be Advisory Circular 107, Pilot’s Handbook of Aeronautical Knowledge and the Aeronautical Information Manual.
4. When we take the test we will be given a Supplement that will contain charts, etc. This will be referred to in many questions (e.g., for Q1 "Refer to FAA-CT-8080-2G, Figure 21.") I tried to upload the "G" version, but I exceeded the limit on uploads. I will upload it to a new message; you can get it at faa.gov. We might get this version, or a new "H" version. So, consider this as practice only.
5. The online course is fine so far as it goes -- it only covers the stuff that a Part 61 pilot would not have already been tested on in their exam.
Some important observations:
a. There is no way that you can read the PHAK or AIM from cover to cover. They are too big, and there is far too much material unrelated to the test. In particular PHAK reads like a miserable excuse for a physics book, and is written in a pedantic tone in the passive voice. I plan to make a listing correlating the Airman Certification Standards to AIM and PHAK and promise to upload it here.
b. Don't give up and don't despair. If you don't pass you can retake the test in 14 days, and they will give you a code as to which sections of the ACS you need to study.
c. Whoever invented all these acronyms deserves a special place in Hell.
Good luck!