Working on PC level repairs does not require a high level of maths or physics, as the equiment is modular, and based on a common architecture (X86) which uses plug and play / industry standard components.
I suggest you look at the ICDL, and A+ Certification courses as a start.
Keep a healthy eye on the forums up the top, look at building an entry level PC yourself, with some help from a friend, and seek advice and support from the forums as you progress.
Good luck with your choice of profession.