Some years ago I looked into fixing a beloved flash unit. The problem I encountered was trying to get a capacitor that would fit in the space of the old one. The ones that would work electronically would not fit geometrically. I came to the conclusion that it was just not worth the trouble.
BTW, even the charge in a weakened capacitor can be very dangerous. All the is necessary to stop your heart is a few milliamperes of current propertly delivered.