Very well, I looked into it, and it's pretty silly.
Bombs: LEVEL: 8! IIn the lower-left part of the 'X'', there is a room filled with yellow sand and grey leevers. You must kill all of the to reveal the bomb item, needed to use bombs.
The hammer is for sale in a shop for 150 rupees.
The3 shop entrance is on A SCREEN WITH THREE GREEN HOOKSHOT POSTS. While these are seemingly pointless, you need to use the hookshot on one of them (the rightmost of the three) to make a door appear, and inside is a shop with the hammer, the flippers and Faerore's Wind.
The Deku key is inside the dungeon, in a kill all enemies room. It's literally in the same room as the boss door--the room filled with LikeLikes and conveyor floors. Good luck there. This quest is idiotic like that.
Why in the name of sanity, of all the quests that you could choose, did this one strike your fancy, again?
Anyway, GL, have fun, and don't gouge anyone's eyes out in the process.