IIRC there is not a huge difference in quest rewards between how you handle the ghost. If you help him he will fight with you against Keara; if not, he will attack you. I think I was level 34 or 35 when I got there, and didn't have any trouble with them.
Do you have your creature summoned to help? I found it was much more helpful with a ranger head than warrior, and best with a mage head.
I forget what level Keara is, but you could return later. If you have not been to all the merchants since the last time you leveled, you could go check for equipment upgrades, etc. The merchant in High Hall starts carrying legendary quality equipment when you get to level 30, but the best ones to check would be the two in Aleroth.
Do you have a spare skill point you could put into Hide in Shadows? That could let your creature handle Keara, or simply give you time to attack and withdraw before getting overwhelmed.
If you are playing a mage, maybe run/jump around like a madman, casting Firewall and Magic Missiles.
