How do you open it?

I'm thinking about building a new front wheel. I built a couple rear wheels a few years ago. Someone asked if I had regreased the hubs. No... Because they were brand new hubs. i didn't think I needed to.

What's involved with opening a hub and regreasing it?

I know the rim -- Same as the rear. I found the right front hub I think. I'm not 100% sure on the spoke lengths, so I figured I get the hub first and measure it myself.