You are not the first, and you won't be the last person to cry at work. It happens. It has happened to me. What matters is how you come back from it.
Break the problem down into manageable chunks and put together an action plan.
If you do not know where things are kept, ask. You are not being a nuisance. Make notes, so you have a reference sheet to go to which will avoid you asking more than once.
Write a list of areas where you feel inadequately briefed to fulfil your role, and ask for help in these areas. Again make notes.
Anything else, ask, and make notes.
It is amazing the difference writing stuff down makes as it provides a framework, and it will help you identify whether issues that are worrying you are new, or something you can do if you look back at your notes.
Don't go off sick, return to work tomorrow with a can do attitude and an action plan. You'll gain respect that way.