How Do You Manage Complexity as a PO?

I think we've all been there. A question is what you do with it. I remember the first time that I worked on somewhat technical product, a data type product. And I felt very inadequate. It's frightening if you hit the first time. You know, build versus buy decisions. We had that with Vodafone. Well, how do you take those decisions? How do you evaluate if that service provider A performs better than the service provider B? What do you challenge them on?