What is the best advice you could give someone during their first month at Optum?

Ask a lot of questions, and if it's genuine, take an interest in the people you're working with. Optum is big and complicated and not always logical, so you're going to be puzzled a lot, especially early on. Be humble, don't assume the weird stuff you see is a result of incompetence on behalf of your new colleagues; they might be able to give you some context. Also, take a lot of time to go over your benefits, because if your better half gets insurance through work it's almost certainly better than what you're considering signing up for here.

Welcome to independent learning