I just submitted my first app last night as well. I had NO clue how to do it other than it "was going to be a pain".
The good news, I have an account with Lynda.com and they have a chapter that is all video tutorials on how to submit the app. It collectively is about a 30 minute chapter with video demos of EXACTLY what to do. Step by step. They offer a free 7 day trial. I cannot recommend you watch this chapter highly enough. Its a MUST see for a first time submission. And no, I do not work for them or associated to them what so ever. They just have a great product and I do not hesitate to recommend them.
After you submit you can cancel your account before being charged.
You can see an example of how they teach w/videos by clicking the link below.
http://www.lynda.com/iOS-SDK-4-tutorials/distributing-ios-applications-through-the-app-store/77853-2.html
They will allow you to watch 1 or two videos, but must sign up on the trial version to see the rest of them.
Trial version link:
http://www.lynda.com/promo/trial/Default.aspx?lpk35=1854
Happy coding! :)