The biggest issue I had was the first week with two females!
It was HECK! Rosie was pissed and she made sure we all knew it! However that didn't last forever. And with you getting a boy I think it will be fine.
As far as feeding, grooming, pottying, etc. I did everything together with my girls. And yes they both drink from the same water bowl. Everything the same except Rosie gets everything first. She was here first so we tend to her first. When I'm gone my son says they sleep together. And the play!! Man you will love watching the two play together!
Now, the changes for me! It is harder taking two places. It has been an adjustment for me. And twice the dresses!
I wouldn't trade having two ever. I'll always have two now. But two is my limit! I think you will love having another addition!