Don't worry about how much you did wrong,remember what you did right,because as long as your players have fun,you did it right.I am also a first time DM but I have a great friend who has been DMing for a veary long time and he helps me out,an easy way to make a great game is to talk to your players and see what they want out of the DM,thats how I do it and my players are happy and love to play my game.
congrats may it be the start of a long and storied career.
Its always fun to start your first game. And its okay to be wrong...just keep in mind that if you make a rules choice, keep the same rule throughout the session. Players won't mind, if its the same for them as for the monsters ( as long as no one dies ). Then after you follow up with it, make corrections, and give extra rewards to make up any greivous errors. Your players will appreciate it more, and come to enjoy the fact that you keep your game moving.
Remember... Its Role-Playing... NOT 'Rule'-Playing
The big question though is "Did you and your players have a good time?"
If I'm remembering the name correctly, you've posted under Kyle's thread about being a 1st time DM, right?
Some of us mentioned that it takes time as a DM, and as a player, to feel comfortable with everything. Mistakes are bound to happen, even sometimes when you've been playing for a while. But as long as you all had fun, that's the bottom line!