So far as we can find out, there is no connection between Agar's Laboratory and any quest. It's a straight dungeon bash for the experience and the treasure. It's not difficult apart from the quality and number of the monsters you meet, but as Zedd says, once you've fallen down that first trap, the only ways out are Town Portal, Lloyd's Beacon, or the back door. Sorry about that. If your party is not strong, I recommend liberal use of Ring of Fire in the side-rooms, and don't be too hasty in going round corners in some of the later rooms.

Incidentally, as long as you're in there for the treasure, you might do a quick search of the chandeliers...