Searching/Editing XML using Linq

I have some XML(see below) that I want to parse using Linq in C#.NET.  I want to:

1. Count the number of hardware nodes
2. Read the value for each CardID under each Hardware node
3. Change the CardModel value under each Hardware node

I apologize for this over simplified version of what I am trying to accomplish, but I believe this hits on all the points.

I have tried the following code to simply count the hardware nodes, but the query contains no elements.

XElement root = XElement.Load(myXMLPath);
            var query = from c in root.Elements("Hardware")
                        select c;

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Example XML

<MyDataSet xmlns="http://tempuri.org/MyDataSet.xsd">
     <Hardware>
          <CardID>0</CardID>
          <CardPCISlot>0</CardPCISlot>
          <CardModel>130</CardModel>
     </Hardware>
     <Hardware>
          <CardID>1</CardID>
          <CardPCISlot>2</CardPCISlot>
          <CardModel>145</CardModel>
     </Hardware>
</MyDataSet>

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