Hi Kumar,
I removed both of my defrost ducts some time ago but can’t remember the exact details I’m afraid other than the fact that the job was a real pain. However, I can recall that I did remove the steering wheel but left the column in place and eventually decided that I didn’t need to remove the steering wheel after all. I also remember removing just about everything from behind the dash, again not all of which was necessary, and still having to manipulate the thing out. Best of luck, just keep trying as it will come out and perhaps someone who’s done the job more recently may chip in.
David Brough
1969 280SL Auto with A/C & 3.46 Axle