I usually complete that quest at level 2 and kill all ghosts and skeleton all the way through the corpse to get the ring for GriseldaWell, I get her early too, usually being lvl 2 without fighting that ghost, wearing no equipment except that I've found, just to "rob" her and continue to do some nearby quests like mirmeks and coyotes.
As I wrote, lvl is suggested by the lowest level of the strongest enemy encountered through walkthrough, so that quest is recommended to complete at 4th lvl to be absolutely sure that any character can beat it without any possible cheesing. But check also H rating, some quests like web of terror can still be hard to complete.
And still remember to check enemies you will encounter to prepare yourself to face, for example, huge ( for lvl 5) poison damage from ghouls in "Where did I put my sword...". Maybe you'll want to delay that quest because of lack of resistance/health/damage.
I think if large enemy groups should also increase difficulty rating?