WCF Services .Net C# searching XML document

I'm looking to create two search services via .Net framework and WCF Service Application in Visual Studio using C#. 1.) Web operation “search” - parameters will include 1) URL of an .xml file & 2) a key (i.e. model or year of a car) a Output: It returns the node’s content information related to the search key, for example: owner, VIN, model, etc. I also would like to read any attributes and if there are multiple occurrences, return all them. Preferably would like to use DOM, but am open to SAX model. 2.) Web operation “XPathSearch” parameters include 1) URL of an .xml file & 2) a path expression output: returns the path expression value of the given path. It could be a list of nodes, the content value, etc., depending on the path given. Preferably would like to use DOM, but am open to SAX model.