I have an EOS 300D, and today while taking some pictures outside it called it quits on me (kind of). I was taking some pictures with high shutter speeds and during one of the pictures the camera seemingly 'locked up'. I waited a few moments, and the camera never finished it's exposure, the mirror never came back down. I shut the camera off with the power switch and that did no good. So I slipped the battery out. When I turned the camera back on, the next pictures started coming out exposed on only one side.
I put the camera into cleaning mode and saw that a mirror, behind the main mirror wasn't going up like it should, obviously causing the sensor to be blocked. I don't know what this part is called, but I have some pictures attached that were taken with my phone.
I'm wondering if anyone may have an idea of what the right terminology is for what's wrong, and what sort of repair costs I might be looking at, or if there's any repair I can do at home.
The one thing I did try, a quick flip of the secondary mirror back up, and it went up okay, but then there was horrible ghosting through the viewfinder and I could not autofocus. I flipped it to manual focus, and for two frames my pictures came out, because the secondary mirror was stuck in the up instead of down position.
Pictures attached, thanks for the advice/hints!
The 'effect'
The cause, in cleaning mode:





