the PI exams arent all that difficult, just read over the notes that you take and all should fall into place, you dont acctually have to know the chemicals, just how to read MSDS adn labels and stuff.
i did my work placement during harvest for a contractor, so i got to lap around the paddocks on a big headder for 12 hours straight for 3 days. great fun!!
if the magnet is in the aircraft, no. the motor is an internal combustion engine which does not rely on magnets and electric currents to power it. if all eletrical equiptment fails, the plane can still be landed. there is a manual over ride for gear, and the rest can be done with the controls...