You can try repairing the Praktica with a metal shutter if the camera is having issues with slow shutter speeds or the self-timer. If you have a camera that does not cock the shutter at the end of the film advance cycle, I would not try to fix it. MTL series is easier to work with.
Camera repair and camera instruction manuals. If you would like to buy the manuals but the links are gone, please write. I can update the links.