Ok, I am a little biased too, since I am a Doula. But you mentioned it being such an intimate time. Just remember that you will have all kinds of different hospital personnel in and out of your room. And hopefully the Doula can help you to not have any casual observers. I guess to me, the benefits of having a Doula definitely outweigh having the presence of an extra person.
About the money, I believe that every woman who wants a Doula should have one. So I have done some births for little or no money at all. Just tell her what you can afford and see if she would be willing to take it.
And I agree with everything nothing_but_cloth said. Interview as many as it takes until you feel like you have found the right match for you.
Oh, and if you are going with an OB this time, definitely have a birth plan! Maybe you can find a Doula who will help you with one.
Joy, Mama of 2 girls, H (10/04)
ISO Munki Fireflies knit fabric!