Disassemble Ithaca featherlite shotgun?

If you are talking about complete disassembly you should probably buy yourself a copy of "The Gun Digest Book Firearm Assembly Part 5: Shotguns" by DBI Books, inc.

If all you want to do is remove the barrel then after activating the safety turn the magazine end cap clockwise until it stops then turn the barrel 90 degrees clockwise and remove. You can certainly continue disassembly if you want to try as this is not a complacated shotgun. The description to do so though is quite lengthy.

I am assuming you are taking abouit either a Model #37 or a M#87