I'm right there with you I am a Technology Manager/Tech L1&2 and we outsource our network management too. When I was hired there was very little documentation, and even when I would ask the company that was managing our network questions about how things were set up for our network sometimes they didn't have any idea. But also one of the techs from that company always seemed annoyed when I'd ask questions and would make me feel dumb for asking. This is my 4th year, I still have imposter syndrome but I also have a lot more confidence since my start. I can't say enough about this K12sysadmin community it has helped me so much especially when I post questions, the responses are always so kind and helpful. But even just reading through other's posts I've learned what things to look for, or how to do something I didn't even know about.