First wheel? I'm too lazy to check out your answers, but considering who your responders are, I'd trust their judgement.
Smart move to double check spoke length 1. Starting with good components for your first wheel build will eliminate a lot of issues. 2. Don't be in too big of a hurry to bring the wheel up to tension. Build up the tension in small even steps to keep the rim round as you go.
Just do it! You'll be fine.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.