A., This will be the most adjustment in your growing family; baby number 2. Now, take heart, once you realize it isn't THAT bad, you'll have a lot of confidence and hope for any future children.
Do things WITH your older child. When you nurse your baby, have your older one get a couple of books and read stories to her while your baby is filling her tummy.
At nap time, have your little girl get a book, go into her room, sit in a chair and read to her with baby and then sing to her--it just does NOT matter if you think you sing well, children ALWAYS think you're a STAR!!
Since you're needing to rest and recover, too, you should make sure your daughter knows it's nap-time for EVERYONE and then when you leave her room--GO TO BED!!
Think about TOMORROW's dinner today--even better, plan them out a week in advance or more. (this will save time and money,too) This is summer, so everything can be super simple--salad, salad, salad. If you have ANY kind of grill, plan for BBQ something where hubby can be the King of Meat and Burnt Offerings!...most men LOVE to grill.
Let you're daughter know this is HER baby, too. Give her some ownership of baby and include her in the caretaking. This will reduce (not eliminate) any sibling rivalry and feelings of displacement by you're older child.
Bedtime and bathtime don't need to be difficult or complicated if Daddy is doing his job of being a Daddy and not just some guy home from work living with some woman who has kids. Give Daddy the baby and go bath your daughter or have Daddy do bath and bedtime--trade off.
As far as baby bedtime...that is all a matter of philosophy, you'll have to decide that. I, myself, am a cosleeper--I'm not going to get up a million times a night to sit in a chair to nurse and I REFUSE to let my babies cry for hours on end until they give up on me to sleep...so, cosleeping with me until --well, until the magical change of the moon when we all know it time for them to be in their own bed, it was a little different for each of them but I've never had a forever child in my bed! lol
You have to decide what is right for your family and what you're willing to do and not do.
At this point you need to have minimum standards for yourself; today I will feel accomplished if dinner is on the table when hubby gets home and ANYTHING else is bonus, or I'll feel accomplished if I've gone outside, the floor is vacuumed and dinner is at least started, or I'll feel accomplished if I'm out of my pajamas and I've actually brushed my hair...slowly increase yourself upward each week or two, avoid at all costs overdoing it--that is a sure way to cause yourself setbacks and prick an onset of depression...from fatigue, frustration, and a sense of failure.
EAT well, lots of veggies, protein (not just meat) and continue your suppliments--even though you're not pregnant, you're still growing a baby.
DRINK lots of water--dehydration will manifest itself in depressive feelings, hungar, fatigue, headaches, moodiness, sleep disturbances, nursing issues like lower supply or clogged ducts, etc...
Have simple snacks ready to go during the day for you and your daughter while you nurse your baby: cut up apples, baby carrots, oranges, bananas and graham crackers, celery and peanut butter...
You're going to have this down in no time, you'll see...!