I'm glad you bought the ergo, I really think it will make a big difference. My high needs son did not like carriers until 4 months and after buying four different ones, the ergo is by far the one we use the most. High needs babies really need so much "touch" and I still wear my one year old a lot, especially when he's cranky. It really calms him down. One tip with the ergo- some hn babes prefer to face outwards which you can't do in most carriers. What we do is use the side hip position a lot. He loves it and now he's heavy, it's easier on my back.
Naps were hard for us too. We had huge success with a hammock until 5 months when he wanted to turn over and sleep on his tummy. I then had to wear him down (I enjoyed this - I'd take a walk) and with time learned how to transfer us both to the bed. To keep him asleep I would have to lie us both down together and stay touching him. Unfortunately, you have to pretty much give up the notion of getting things done with a hn baby. But it does get easier. I still nap with ds and get things done on my iPhone, which also has kindle so I can read books.
One more thing, if she doesn't take to the ergo right away, just keep trying a bit each day and keep moving. Ds doesn't like to be still ever!
Let us know how you get on.