A camera flash that isn't going to have enough amperage to kill you, but it can bite pretty hard (been there). If you get shocked by it, you might swear off working on it again - and you will probably swear.
It is easy to short a cap to discharge it, and then you will be safe.
The worse part would be trying to de-solder the capacitor, then solder a new one in, without damaging the unit with the soldering iron. I've not fixed a flash, but there is not a lot of room to work with.
That said, I'd just load some batteries like you intend. There is a good chance the unit will be fine.