Yep, It screws out and I would be very surprised if that one does. Cut it like Tim and dan say. You can try to unscrew it first with the 2x4 idea it's a good one. But if you try to hard you toast the plastic tank.
You may need a new one anyway. i would be surprised if that one is in good shape. Andy at inland RV has nice fiberglass replacements. Not cheap but I'm happy with mine.
May you have at least one sunny day, and a soft chair to sit in..
2008 5.7 L V8 Sequoia
AIR # 31243
WBCCI # 6987
FOUR CORNERS UNIT