By panel I assume you mean the glass! Remove glazing bars (internal or external) with a scraper; remove the glass (marking the inside before you remove) & packers; re-fit glass & packers the same way they came out; attempt to re-fit glazing bars – not always easy if you’ve not done it before. Plus there is a risk that if the windows are more than a couple of years old, the rubber seals will be prone to damage & will then let water.
If you don’t need the sofa any more, I would cut it up & take it out the door!
Some units use stainless steel screws; remove the screws & the hinges come off with the window. If yours are riveted it means drilling out the rivets & if the rivets are stainless steel they will be fairly hard so it needs to be done carefully to avoid making a complete mess of the rivet holes in the frame. You will obviously need replacement rivets & a good rivet gun to re-fix the hinges.