C# - How To Modify A Web.config File As If It Was A Text File

by looking at using the XmlDocument and creating elements and attributes and then inserting them into the document. Pretty soon this looked like a massive amount of work for all the elements I have to add.What are the repercussions of treating the config file as one big long text string and doing a replace at certain points to add my entries. Something like this...

private void InsertXMLElement()
{
StringBuilder webConfig = new StringBuilder();
// get the file into a stringbuilder for manipulation
using (var sr = new StreamReader("C:web.config"))
{
webConfig.Append(sr.ReadToEnd());