If you want guidance on converting TEI documents from SGML to XML, here's the FAQ . There are lots of sources of information for SGML and, even more so, XML tools on the web. This setup was last updated on June 11th 2001. Comes with an easy form-filling interface . PassiveTex is a generic processor for XML FOs, using TeX as a backend, includes several TEI customizations.
Instructions are available in English and Russian.