A couple of days ago, I was taking a picture, when after pressing the shutter button I heard a loud pop and the camera wouldn't turn on anymore. Thinking it was a battery problem, I changed the batter and it turned on. But when I went to take pictures, it showed Err 99 and it didn't sound right. I took off the lens and saw that none of the mirrors were going up when I pressed the shutter. The main mirror moved a fraction of a centimetre before falling back into place. For longer exposures or sensor cleaning mode, the mirror goes up for that fraction of a centimetre and stays there, before finally falling back at the end of the exposure or when I turn the camera off. Nudging the mirror to help it on its way up doesn't work.
What should be my course of action?
If its a broken pin or something like that, I am willing to fix it by myself.