Head to The Elddar Grove in Qeynos Province District. The Guards are level 55 at the gates, Lower level characters can avoid the guards by going through the Peat bog to the Vermin's Snye to Down Below, then the Elddar Grove.
Click on the basement doors outside the In Range ammo shop in the Elddar Grove at Loc (575, -18, -398) and enter the instance The Seed of Tunarbos.
When you zone in there will be several aggressive creatures near the entrance.
You can invisible or stealth past most of the monsters in this instance.
You can avoid fighting all but 3 mobs with invis/stealth or Chameleon potions and careful movement. Kill the 2 plants by the entrance. Grab the oil from as far away as allowable. Invis and head upstairs. Kill the Warden for the key. Unlock door, detonate the barrel and run out of the instance. 10 minutes and two or three invis Tops.
Don't assume your Invisibility will hold up when zoning into the instance. More often than not, it doesn't hold.
The table on the first floor is clickable but doesn't appear to serve any purpose for this quest.