Yeah, just hit them. They'll die rather soon with your Excalibur (have you remember to #enhance your weapon skill?). And remember to be in the stairway, so that they can't escape (they only try to go up, never down). I suppose sleep doesn't work, but it's worth a try. Oh and it's +6 or +7. If you're lucky, enchanting the weapon when it's +5 with a blessed scroll might make it +7. But never enchant a weapon over +5, there is a great chance for it to vanish. (The same goes for armor over +3, or elven armor over +5.)
The Wizard of Yendor (aka Rodney) is pretty tough and annoying. He will be stealing some of your artifacts (the quest artifact, the bell of opening...). Once you kill him the first time, you'll get the Book of the Dead. Try not to kill him above water, since then the book will be hard to get. However Rodney will be haunting you later on too, he wouldn't be a higly powered wizard otherwise.
"Once killed, the Wizard of Yendor will be causing trouble to you for the rest of the game. He resurrects as a little stronger incarnation every time you kill him, level teleports after you, summons nasties, will curse your items, and will try to steal the Amulet of Yendor if you have it. Perhaps the most menacing spell the wizard can cast is Double trouble, which creates a clone of the wizard himself."
He can be killed with a wand of death.
Oh and you won't be facing Moloch, you'd have no chance against a god. In the bottom level, however, there is the high priest(ess) of Moloch, who carries the Amulet of Yendor ( 8O ). He ain't too hard if you have reflection, but the bottom level itself will make you some hard work. There are many priests of Moloch, and they will summon you some trouble. Rodney will be there too, so you're going to have to be prepared with loads of healing potions and charges with the wand of death. (Of course you can just fight them all down but it ain't gonna be easy.)