Congratulations Wally!! that's really brilliant news, especially after the hard time you've been having!! Don't worry about all the people who will be there (although I know that you will anyway :-) ) just remember that you know more about your project than anyone else and if they come up with some suggestions or things that you've not thought of it's a good thing, and better at a conference than your viva! ;-)
I'm just back from my first conference presentation myself, and after spending weeks freaking out about it, and a very tense 2 days stalking my supervisor getting him to check my talk, I had quite a lot of rescue remedy before my talk and it went went really well! There were lots of expert people in the audience, including the 'Yoda' of my field who was sitting in the front row assessing the talk (bloody scary), and I ended up winning a prize for best student talk! So just stay calm and you've got lots of time to prepare for it and you'll be great! Congrats again!(up)