I'd echo much that has already been said.
It does hurt in the beginning and expecting it not to means that you just feel like you're doing it wrong if it doesn't feel comfortable to start with.
The first 6 weeks is a real milestone. I spent the first few weeks going from day to day, then week to week i.e. "I'll just try it for one more day, then see how I feel". After a week, "ok, I'll just keep going for one more week, then I'll re-evaluate again"
Success in expressing can really depend on the pump. I had loan of a fab one from local hospital, so my advice to OP would be to know what resources are available.
Nipple Shields - I apparently have very flat nipples. Didn't find out till midwife said "you'll have serious problems feeding with those" (Thanks for the help!!) Afterwards a more patient midwife explained what I could do and encouraged me to use nipple shields and where hubby could buy some (they had some you could buy in the maternity unit - v helpful). In the meantime dd was getting very jaundiced, so they also helped me cup feed formula. So, like others have said, I think it's important to know that a little bit of formula in the first few days will not prevent you from mastering the breastfeeding.
10pmish feed - In my experience, this feed is when I felt I didn't have enough milk for dd and yet it's the feed when you want to 'fill-up' the baby, in the hope they'll settle for a good few hours sleep. I found expressing in the morning, when I seemed to have lots of milk and then letting dh use this expressed milk to 'top-up' dd after I'd fed as much as I could at 10pm helped us.
I also went to a breastfeeding group every week, which is where I met people who are now good friends. It was in same place as baby clinic, so partly just a good chance to get out and about in the first few weeks. If, OP, as a peer supporter could attend these groups, let new mums know about them, or even set one up if there are none it would probably be a good experience.
best of luck - sounds like you'll do a fab job.