You can find deck plans right here on the DIS. Near the top of this page is a red menu bar. Select "Ships" and "Deck Plans" from the drop down menu.
You'll find that the cabin numbers are laid out logically on board so don't stress about finding the FE cabins. The numbering scheme on the Fantasy is each cabin has a 4 or 5 digit number. (Cabins on Deck 10 and up are 5 digits). The 3rd number from the right is either a 0, 1, 5 or 6. A 0 or 1 indicates a cabin on the port (left) side of the ship. A 5 or 6 is a cabin on the starboard (right) side of the ship. The last two numbers are sequential running from the bow (front) to the stern (aft or back).