Removal Pre-fabricated Fireplace

My apologies if I get the jargon wrong. I will do my best to explain.

Our family room was built with what I believe is a pre-fabricated fireplace: hearth with a metal flue that runs out the side of the house. The house has a wood box built on the side with the flue running to the top. The flue is capped. I have removed everything except the flue that was connected. The flue comes down from the wall at an angle. There is flashing around the flue where it comes out the wall, which I have not opened yet.

Question, is it possible to disconnect the angled portion and leave the rest, or do I have to remove the flue all together? As well, does anyone know if removing the angle piece easy or difficult? The flue does feels heavy. Thanks,