Hu Judypru,
My flight was actually longer than that haha
I booked my flight quite late so I didn't have many options. I had to fly from Seoul to China which took 4 hours. Then from China to Amsterdam which took over 12 hours!! and the last flight was from Amsterdam to Copenhagen which was an hour.. I was very worried about the long flight, I remember getting a panic attack when the flight between china and the Netherlands was taking off. I just felt my feet swelling up because I couldn't elevate and knew it was going to be a hard flight. They gave me a good seat. I had sooo much legroom but that didn't help because I still could not elevate. After like two or three hours a man got upgraded to first class because his words "He can sleep vertically he needs to lie horizontal".. So he came up to me and said I can take his old seat, which was in the back. There were 3 empty seats just for me which sounds good but the armrests didn't go all the way up so it was impossible to sleep comfortable anyway. I got a bit annoyed that they didn't upgrade me since one of the flight attendants knew my condition.. But whatever..
About airport assistance. I sent an email to China southern (airline) and asked for assistance at the airport. You can also write your airline on Facebook, I noticed you gat an answer quicker! I also asked Dr Park to write a doctors note incase the airline needed it which they didn't. Then when I arrived at the airport I just informed the someone the the checkin counter that I had arrived. Later someone that worked at the airport picked me up in a wheelchair and this was very cool because we took a lot of shortcuts, cuts lines and it all went quick and smooth, no big lines and all that. This is really great, someone picks up up and drops you off, you don't have to worry about anything. I remember getting stressed because takeoff was getting closer and I had still not gone trough airport security. But as I mentioned before we go in a special line and cut before others. You will either be picked up in a wheelchair or a electric little "golfcar". In Seoul and China it was a wheelchair in Amsterdam and Copenhagen it was a electric car. I defiantly recommend getting the assistans!!