The maths is minimal and you can use a calculator in the exams anyway. The most important thing is to get used to doing mental sums, because in a real situation when flying you aren't going to start digging a calculator out of your bag. I would say that the emphasis really should be on situational awareness and how the wind is affecting your flight and take off/landing. It's just very basic trig and there are totally idiot proof simple ways of calculating stuff like that which your instructor will show you.
Also you say you haven't started the actual flying yet so it wouldn't hurt while you're driving just to do a few simple time/distance calculations IE 'I'm on the motorway doing 70mph and it's 20 miles to my turn off, how long is it going to take me?' and then actually time yourself to see if you get it right. I know it's rare to be able to keep a constant speed but even so, if you arrive late or early at your turn off try and work out what your actual speed was. It's exactly the sort of thing you'll be doing in your nav exercises.
Edit: Oh and don't worry, if you have the brains to put food on a fork and not miss your mouth then you have the brains to be a pilot...There's a lot of mythology about being a pilot, one of them being that you need to be some kind of superman. Once you have been on here a while you'll soon realise otherwise....
Edit 2: Just seen that you're 17 and may not be driving yet...see we're all idiots really
