Yes, it is assembled. Remove and replace. I don't think the Honda one comes with new screws. Use the old screws.
The last time I bought the Oberon brand one, the ad said it came with new screws. The screws weren't correct so I used the old screws.
I had a clean master cylinder, hose and new slave cylinder. I adjusted the MC to as horizontal as possible and filled to close to the top. I got a couple rags and a bleeder size wrench. Don't pump the lever. Crack the bleeder valve open about 1/8 turn. Within a few minutes fluid will start flowing out the bleeder. Wipe it dry a couple times and when the fluid bubbles stop, tighten the bleeder valve. You're probably good to go.
