Canon 300D problems

I have a canon 300D, whilst on holiday I took some shots and when reviewing them they was only 1/3 of the picture showing, the rest was black. The secondary mirror was sticking down. A good clean off later, I am getting full frame pictures, but the auto focus is trying to focus, but is not truly focusing. I have now treated myself to the new 5Dmk111 (still trying to figure this computerised genius out), but would like to pass my 300D onto a young student whom is very keen to learn & has a very good eye for photography but they cannot afford a decent camera. Is it worth repairing & any idea on cost.
Many thanks,