XML beginners Q's?

Ok I’ve read quite a bit about XML on and off for a year or so, but have shyed away from it until now.

I am currently working on a personal project which I have decided to use XML.

Now I have a few questions about XML specifically:

1 - How do I include the & symbol in my documents
2 - How do I link to external sites as I would in a HTML doc?
3 - I have a field in the XML doc named date, I want to sort the date field by date ASC, but how would I specify this in the XSL?

My next query really centres about how everything fits together, at the moment I have a HTML doc, CSS, XML, XSL.

Obviously the HTML, CSS will provide the presentation, XSL will provide the HTML formatting but how do I display the XML date in the HTML doc - do I need to use a Server Side Language and if so how?

Sorry for all the questions.