That's right. Vengeance, unfinished business, the whole nine yards. The case I'm looking at reads like a marriage with a hell of a lotta foul play, so I'm thinking them family would be the best place to start digging on this one. You find the family, you find your answers. Should be pretty clean cut, if you can actually work them enough to get the truth out.
Which brings me to my first question: have you ever roleplayed before?
Magic and healing items aren't gonna do much good for you here. You've got your rock salt and silver to defend yourself with, which'll send them away briefly if they attack you (while simultaneously pissing them off). Likewise, the rock salt is as good for keeping you safe against them the same way you'd use it for your typical protections around here. Draw up a circle, step in it, and the spirit can't touch you.
And then, of course, there's getting rid of the spirit for good. I really hope you're not squeamish.