The cursed abbey may be a little difficult until you are in the high teens for character level. If you have cleared the area around Aleroth and explored the farmlands and east of there, the next easiest area would probably be to the north east. After that, the north west area around the cursed abbey should be doable; the undead there are slow (easier to take out from a distance) and do poison damage (if you see any Spell Shield books for sale, buy them - poison damage comes off the shield and you do not jerk around). You can probably clear some of the area to the south, but the stronger orcs or trolls would be pretty tough at your level.
