Yes, a double electric breast pump is a must if you wish to continue breastfeeding as a full-time employee. My daughter is 4 months old and I've been back at work for 1 month now and it's been going well. I pump twice a day while I work. I would recommend that you only freeze the milk that you know you won't use for 2 or more days because freezing kills some of the good stuff. If you're overwhelmed by the cost of a decent breast pump don't forget that you can rent them, which is probably the best idea. The best types are available at an amazing store for breatfeeding moms called Baby, Mother and More in Chandler. You can rent them for something like $30/month.
Regarding the need to eat all the time, just like some of the other ladies, I found that waking her after each side with a diaper change helped her to eat a bit more and feel satisfied for longer. I also found that sometimes she was just needing to suck on something so I would give her my finger because she wasn't too fond of the pacifier. I've also heard though that it's very important not to give the pacifier when the baby is truly hungry just to buy a little more time. It should only be used for the need to suck. I hope that some of this helps you with your little girl.