You don't have to go through all of these resources. Consult the resources you need when you need them.
This website contains documentation for the NX 1899 series (note: this website is for an older version of the software, but a lot of the information contained here is still relevant).
This website hosted by NASA is a great resource for all things Nastran (note: Nastran is the name of the solver that NX uses). It contains a section on finite element model validity checks.
This discussion board may be a useful place to find answers to some of your questions. It also contains a link to articles covering different simulation topics.
NX CAD Design Certification: https://blogs.sw.siemens.com/academic/students-get-nx-cad-design-certification-free/
Resources provided by Siemens NX: Link, link2****
This Google Drive folder contains documentation on NX.
This document explains the NX simulation procedure for the HERON shock simulation and modal analysis.
Articles/Papers
This Google Drive folder contains two recordings of meetings where we troubleshoot the HERON NX.
This [tutorial](http://nx%20meeting%20recordings/) explains how to create an assembly FEM in NX.