Hi, so I took the MCAT quite a few years ago but I'll try to give the best advice I can on the subject. From what I remember, the exam was divided up with a organic sciences, physical sciences, english, and writing portion. I think the exam was somewhere around 6-8 hours with an hour break in the middle somewhere.
So for the organic sciences questions, it was a mixture of biology and O chem. The physical sciences was a mixture of physics and general chemistry, and the english portion just had you reading 7-9 long passages and answering an assortment of questions afterwards. The writing part usually had something like "Two birds with one stone" and you'd have to write an essay about it.
If I could give some advice on preparing for the exam, it would be that over the next few years keep brushing up on the fundamentals of the physical sciences and be an avid and recreational reader. Most of my classmates excelled at the biological sciences but had weaknesses in the physical science portion and the english portion.
I took the MCAT twice, but medical schools prefer that you don't take it multiple times. You have to weigh the risks and benefits of taking it more than once. If you had a horrible first score and took it again and greatly improved, they'll look favorably on it. However, if you got a decent score, took it again and got around the same or lower then it looks bad.
Also medical schools like well rounded students. So if you got a 15 in physical sciences, 15 in organic, but a 5 in the english portion then it looks much work compared to the student that got 11's and 12's in all the subjects. Got any more questions, feel free to PM me.