transform xml tag to css tag in c#

Hi there,
the question is related to C# and XML.

I have simple xml file
<pre:book>
<pre:author> Mark Twain </pre:author>
<pre:title>Tom Sawyer</pre:title>
<pre:chapter>text stuff
<pre:highlight>important stuff</pre:highlight>
more ordinary text
</pre:chapter>
</pre:book>

I have to parse this file and store its elements into database.
In C# I used XmlTextReader because of it's processing speed. There is a part of my code:

XmlTextReader reader = new XmlTextReader(xmlPath);
while (reader.Read()){
if(reader.NodeType == XmlNodeType.Element){
//Get the name of the XML token
switch (reader.Name.ToLower()){
case "pre:author":
saveToDatabase("author",reader.ReadString());
break;
case "pre:title":
saveToDatabase("title",reader.ReadString());
break;
....

In the database I have a column named 'chapter' to store the text from element <chapter>. But I can not use reader.ReadString() method to read text in the element chapter, bacause it reads just to the first <highlight> element. I need method that will change tags <highlight> to <span class="highlight"> inside element <chapter>. The purpose of this trasformation is the ability to get easily "chapter" information from the database and put it on the web using css styles.
I suppose I need to use XSLT transformation (I'm new to xml/xslt) Is there a way to do such a transformation for one node
(<chapter>) on the fly. Or do I need to do the transformation of the whole xml file and after this step to do parsing?

I appreciate any help.