Newbie Question - Granting Playable Character Status Immunity

I've never tried to hack this game before and every piece of advice I've read has said to start small, so I'm starting with what I hope is a trivial question.

I was looking to make a single, permanent playable character immune to a specific negative status. For example, I would like to make Edgar immune to Poison inherently so that he could not be poisoned at all under any circumstances. My questions follow as such:

1. Is this a simple task or an advanced one?
   
2. Would I have to permanently force the equipping of a Relic to achieve this effect or could this be done in a different way?
   
3. Can this be done through good, old-fashioned Hex editing, or will this require ASM work?