If you realize impermanence and cause and effect very strong, no problem; dying is nature.
Passing away is dying, right? If you really understand impermanence, no problem about dying because understanding impermanence is already understanding dying.
You are always dying moment to moment, right?
Only understanding rupa & nama and cause & effect, you are not afraid. If you really understand what is rupa and what is nama, right?
Depends on understanding level; these 2 levels (the first 2 insight knowledges) are enough if you really understand them.