I don't travel particularly far- I've never been in a plane that I can remember (I'm told I was on one once when I was young). What helps the most for stress is planning- know how you're getting from home, to the airport, to the hotel, to the con. If you get there early enough, consider taking the route up to the con site beforehand, just to make sure you've seen the landmarks. If they'll allow it, go inside the conspace & get your bearings a bit.
For meeting celebrities, that part's fairly simple: Follow staff instructions about where to go, if photos are allowed, how many autographs, etc. Don't scream at them, don't get handsy, and limit interaction to a minute or two tops, unless they do something to allow for more, or less, time. When I met Haley Atwood, there was quite the line, so she only had time for a basic 'hi *sign* thanks for coming bye' interaction- I was impressed at how cordial she was, given the short amount of time she had for each person! On the flip side, Reuben Langdon spotted my friend's Vita when we got his autograph, found out he was playing Marvel Vs. Capcom 3, and wanted to try it- so we inadvertently ate up a lot of his time
Most of all though, don't worry about it too much- these people do this for a living, and as long as you're doing the above, you're not likely to upset anyone.
One last thing to keep in mind: Cons are a great place to get a feel for travel, becuase you'll have ready access to a large amount of people who like what you like, and therefore are a great source of help should you find you need it. I've only had one 'con emergency', if you will- we were getting ready to leave the last day of a con, and discovered the car's battery was dead. My friend started panicking, but I stopped her and said "it's ok- there's still hundreds of nerds around us, it's the middle of the day, and we aren't far enough away from your dad that we couldn't call for help. Let's go talk to the parking garage staff." They had a portable battery for jumps, but the car was so dead it wouldn't work. We found some people willing to help, but the car was so dead we couldn't put it into netural to roll it over to their car. Then the people parked across from us came out & we got a jump from them. Over this whole process, people were coming up to ask us what was wrong, can we help, waiting with us to make sure we were OK & looking for other ways to get us moving. If distaster does strike, you will be among friends, so don't sweat it!