Best Practice For Creating Secure, Performing, Multilanguage (read only) XML API To a Drupal Site?

Hi,

As you can see in the title, i am looking for a way to build a xml api to a drupal website.

Description of the Case:

• Customer already has a huge website in Place. He would like to replace his existing FAQ Tool with this solution.
• The Solution should provide
  1. A FAQ Portal with Search, Categories, and Detail View of the Questions/Answers
  2. Content Mangement Backend for the maintenance of the FAQ Content
  3. Everything has to be Multilanguage (three languages)
  4. XML API To insert the FAQ in the existing Website
  5. User Interface to the XML API for the Content Managers to generate XML Links for use in the Pagelets within the existing Website (some Form to create URLs like: "Get 10 FAQs from Category XY in Language RU" -> generate Link)

I found several modules promising xml export/interface of views or nodes.
But "Services" & "Content Distribution" seems to be the strongest solution.

Unfortunately, i couldn't find much documentation or screencasts for the actual stable versions for D6.
(I have to use D6 because the site is multilanguage and it depends on lots of modules wich are not ported to D7 at the moment.)

So my questions are:

• Are there Best Practices, Whitepapers or other Documentation available to provide the mentioned (read only) XML-API to a Drupal Website?
• What is the best starting point to solve this case? Any documentation, screencasts, etc. welcome