Hi H.-
I went through this with my son when he was a year old and now my daughter is going in to daycare and she will be a little over 6 months old. Honestly, the first day and that first week were the hardest. I sat in my car and cried that first day after dropping him off. Every Mom I've talked to about dropping their kids off the first day said they did the same thing. As long as you've chosen a good day care that you feel comfortable with - things will fall in to place.
To transition your daugher (if possible), start taking her to daycare a couple of times a week for a few hours before you have to go back to work. We did this with my son and it was really nice not having the pressure to be in work yet and practice the routine. Not only did I get good lesson in how long prepping him, dressing, traveling, etc took, I also went to the hairdresser and ran other errands in preparation for my job starting. We did the part time schedule for a couple of weeks, then moved to a regular full time schedule. We also shopped for a new lunch bag, new book bag, and a sleeping bag for his new school. Your daughter is the perfect age to make that sort of shopping trip fun for her. You could also drive by and show her the building or bring her in to meet the teachers and kids before she starts.
Your daughter should be fine - and you will be too (after a couple of days) Your daughter will probably surprise you after she adjusts to the new place - she may not want to leave at the end of the day! I wish you the best of luck and hope your daughter has lots of fun.