Nice photo Jay, and nice looking daughter- I don't mean that in the usual way but rather she looks happy and has a good sense of self. It shows in the photo and will serve her well all her life. And that is mostly due to you and mom so congrats and kudos. I am sure she will do fine in the new environment (school) and fit in while steering a reasonable course around some of the excesses that some kids get into when at school.
As far as feeling old, not to worry, you'll get older so this age is just a short portion on the longer journey. :-)
The mom thing can be tough- my first left the house at 18 and went to live with friends, I forget the name..... Oh yeah, the US Army. He turned 18 in August of 2001, signed up for induction in December and received a contract stating he would spend his tour in the US, go to school for XXX, etc. Then Sep 11 happened and the deal changed slightly- he went to basic and then AIT and then was sent to Afghanistan. Mom was not pleased to say the least. After that, home for a bit then Korea, and finally another tour in Afghanistan. The whole thing was pretty tough on his mother but when the second one joined in '06 it got tougher. He spent a tour in Korea and a full tour in Iraq before returning to the US. So I am pretty familiar with having an unhappy / depressed wife (while not being overly happy about it myself). In the end though, both came home intact so all is well and both are now also attending school.
After a fashion you might be lucky and have a few grandkids crashing around the house. I am waiting for that phase myself- my youngest is married and I gave them a booklet with pictures and everything but so far nothing swelling at their house. Unfortunately they are on the entire other side of the country so that will be a mixed blessing also- having grandkids but not being around to really interact with them and get to know them.
Best of luck Jay although I am sure you and your daughter will do well.
Brian
So today we moved our oldest daughter down to University of Oregon for her first year of college, man I forgot how small those rooms are, and she'll have a roomate in that little room. It makes me feel kinda old having a daughter in college now, man time goes fast, and I'm actually already sad knowing she won't be living at home for the first time in her life... 
We are so proud of her though, I know she'll do great away at school, and the one good thing is it's only about 100 miles away, so may have to do some weekend trips to still see her and catch a game. Mama on the other hand isn't taking it too well, lot's of tears saying goodbye... 
Our other daughter is right behind her and in 2 years from now me and mama will be empty nesters but still in our early 40's... 
GO DUCKS!!!
