I think you live in the best possible country to get into this. The WRU is nuts about this. The best thing to do is to get in touch with one of the academy programs.
Qualifications? Did you have some experience using video with a club? Video camera's are not that expensive anymore. Get going and built your CV.
A Level II coaching qualification is a basis. This is the course where you learn about the individual roles and responsibilities of the rugby positions. You will have to rate performance against this.
, I am almost sure that is what the WRU is using.