Mrs, honestly I think the hardest bit is going to be giving your DD1 the time and energy whilst recovering from your c-section.

With DD1 I just made her into my little helper, she just loved doing anything to help her little sister. Yes, she had her jealous moments, especially when I couldnt get something done for her immediately like she was used to in the past. But I solved that by making sure I had food and drink available before I had to do anything with DD2.
Like WannabeMum, DD1 dropped her day sleep 2 days after DD2 was born which made things a lot harder, but thankfully DD2's feed times became really good rest times for DD1.

Dont feel guilty about bringing a new child into your family, but use it as a positive instead. Involve DD1 in as much as she wants to be involved with, use her interest to your advantage. I think as parents we tend to overthink everything, especially when it comes down to bringing another baby into the home. (I personally think bringing a new pet into the home is harder than a newborn sibling.)

Celebrate having another baby in your world, let your DD adjust at her own rate, and relax.