Hey,
The materials posted on GMATClub are more than enough for TOEFL preparation. I prepared for roughly a week before my test and managed to score this much.
The reading section is about an hour long. If you are already preparing for GMAT, you won't find the reading passages tough, very straight forward questions. So, no need to worry about that. Certain difficult words are hyperlinked to their meanings. No worries!
The listening section is also about 60 mins long with 3 sets of questions(each set consisting of 1 conversation and 2 lectures). Though taking notes is not very necessary I would personally recommend it because it helps you concentrate on it better even if you don't refer to them while answering the questions.
Coming to the speaking section- it consists of 6 questions- simply watch the instructional videos posted on this forum.Familiarize yourself with the structure and practice a few of each type. That is all.
Writing- well, just stick to the templates. Make sure your writing is coherent and clear in the idea and organization. I don't think they care too much about great vocabulary or something.
Hope this helps!