ITSM Implementation

Answer:
That depends on many circumstances. But, let's assume you have management commitment and available resources (if not - gaining management commitment is -must have). Our free webinar (recording is available) "How to use a Documentation Toolkit for the implementation of ITIL / ISO 20000 " https://advisera.com/20000academy/webinar/how-to-use-a-documentation-toolkit-for-the-implementation-of-itil-iso-20000-free-webinar-on-demand/ will give you many information that you can use to start your project and answer the question regarding necessary documentation.
Also, the article "12 steps for ISO 20000 implementation" https://advisera.com/20000academy/blog/2016/09/06/12-steps-for-iso20000-implementation/ contains guidance how to approach the implementation.

Regarding training - at least ISO 20000 Foundation is a dvisable. It will give you understanding of the standard's requirements and some hints how to approach the implementation.