Honestly, I find your questions to be quite large-scope and general, even if you might have read even some of the "methodology" and "infrastructure" materials found at the suggested links and follow-on links as well.
For a SAS BI initiative, you have much of the SAS System, with its tools, procedures, and information management facilities, available to develop your SAS-based application environment.
Regarding your SAS DI (Data Integration) questions, I do not understand what you are asking about regarding users? Here is one of several white papers and technical references on the topic, available at the SAS support website - suggest you do some searches for management planning and implementation knowledge and guidance.
I agree with Scott that your questions are really very large scope questions and cannot be answered in the amount of space available in the forum. The links that Scott provided should illustrate for you the overall architecture and capabilities of the BI (or Enterprise Intelligence Platform).
The Desktop client applications (which some might call "tools" ) are clearly shown in the diagram. Among the client applications listed are the SAS Add-in for Microsoft Office and SAS DI Studio and SAS OLAP Cube Studio -- could these all be considered "tools"??? Yes. But in reality, they are client applications whose usage will depend on the job roles of the people using the various client applications. For example -- will a person who works with Sales Reports every day with the SAS Add-in for Microsoft Office ever use SAS DI Studio or SAS OLAP Cube Studio???? Probably NOT.
The end user who access data and creates reports with the SAS Add-in for Microsoft office may use information maps, data tables and OLAP cubes that were specially prepared for them -- but the end user is not involved in the data preparation themselves. Most corporations or sites have "data managers" or "data based administrators" or "data dictionary administrators" who are responsible for maintaining and managing data resources and it is these "data managers" who would primarily use SAS OLAP Cube Studio, SAS DI Studio and, probably, SAS Information Map Studio.
I don't understand your questions about what the users require for SAS DI?? Do you mean for SAS DI Studio??? SAS DI Studio is the client application used by DATA MANAGERS to load data, extract data, and transform data for use by less technical users. SAS DI Studio is a component of the whole Enterprise Intelligence Platform. For specific system requirements, white papers, customer success stories, and market research, see this site: http://www.sas.com/technologies/dw/index.html
Just to add what already has been said: If you want to get into this "technology" and you have none or only little previous knowledge in this area then you need either a helpful and knowledgeable senior colleague or you have to attend several of the SAS trainings.