I am in the middle of doing this now. I took the old one out by pulling it from outside the tank while putting pressure on it from the inside with my finger.
Then I used the old one to experiment with in trying to get it back in the tank. I did not want to have to remove the handle, the choke and throttle linkage , the carb etc. It is a very tight fit to put it back in from the top (at least it is on my MS280). But I was able to force it back in by pushing from the top while gently pulling from inside the tank. Hope it does not damage the new line once I try with the new one.
Cood, May 2011