Hi Livvi1, welcome back and glad to hear that all has gone well with your reconstruction - B1 & B2 - very cute!
I had the fat injection (lipofilling) done in August last year on my reconstructed breast as a seroma had formed after surgery and had to be drained, leaving a noticeable dent at the top of the breast. The lipofilling was fairly straightforward and is usually done as day surgery. I had it under general anaesthetic. They took some extra fat from my hip and injected into the breast. They often put in more fat than needed as it can lose volume over time, but I have to say that mine has done well, and I believe they are refining this process all the time so less fat is lost. I did have some spectacular bruising on my hip for a couple of weeks, and got to wear the gorgeous abdominal binder again for 6 weeks, but other than that, pain was minimal and I was up and about soon after the surgery.
In regards to the nipple: had my reconstruction in late November last year (with a breast lift on the remaining side to even things up) and the nipple part of the surgery was quick, around 30-60 minutes I believe and there was very little pain with the new nipple, but they do require some dedicated post-op care to keep their shape etc. Although most nipples do lose some "projection" over time. Nipple shields or other coverings are used to protect the nipple while it heals. Don't forget to check out the nipple reconstruction stories / photos in the Breast Reconstruction Group, which should give you a good idea of others' experiences and what they did to look after their new arrivals :-)
Of course you might decide not to bother with new nipples, and this is completely up to you. Lots of women decide they've had enough after the initial reconstruction and are happy with their new breast shape. For others, it doesn't feel complete until the nipples and tattoos (separate procedure) are done. The important thing is that you feel happy with whatever decision you make. Best of luck. Jane xx