Tutorial XSLT Transform from XML to XML

Hi,
Using MS Access, I will export data into a XML file but that XML doesn't comply with the XSD schema I am given. Using XSLT transformation, I am planning to transform my first XML into a second XML that will be validated by the schema. I've never done any XSLT transformation before. Where can I find a tutorial with examples to transform from XML to XML ?
Thank you.
Pipo.