Congratulations. I had my first at 18 and have just had my 3rd and last at 31. It's hard no matter what age, I found it as nerve wracking this time as I did back then.
If you have stitches, take a jug of water to pour over yourself when you pee!
Accept all the help you are offered, family are (hopefully) well meaning and it will help you adjust to life with a baby.
The health visitor is only at the end of the phone if you need any advice, that's what they are there for.
Ask a family member to help you out the first time you bath baby- that's probably the thing that worried me the most. They could show you how to (sounds daft but I honestly needed to be shown this) or just be there for moral support.
Leave the umbilical cord well alone- I feel like I always worried about it way too much
Your first night home from hospital will be the worst for you but every subsequent one will be better than the last as you get used to being a mum.
Don't feel pressured in to doing anything you don't feel is right for you or the baby, I feel like this happens a lot regardless of your age.
IF you do find your self struggling ask for help, family/ health visitor/ gp- no one will judge you over it.
Mostly enjoy every second with your baby- it sounds like your making every effort to prepare for the reality of her birth, you will do just fine.
Take all advice with a pinch of salt, including mine, every ones experiences are different. 