Quick tip for anyone just getting started (this means you, adrian1). Always save just before leaving town. You will die a lot in the early phases of the game. To save, hit the little "x" below the town name. then press the icon in the lower right corner that looks like a wrench. The save menu will come up. Save early, save often.
To sell items, you must find a portal scroll in one of the treasure chests. That will transport you to a shop where you can buy/sell stuff. Once you have enough cash you can also buy a preferred customer badge that allows a free trip to the shop once per level.
Just beat a pandora's box of 3 gorgons, 2 minotaurs and an undead boss. Took an hour and the loot drop was nothing special. You can beat almost any combo with a warrior who has enough armor to reduce damage by 99% when you use speed, damage and poison resist buffs.