XML and JTrees

Has anyone got a example of putting a xml document into a JTree then selecting the record in the subnode of the jtree by its unique id, to copy the information from that jtree unique id into jtextfields.  

Then once the jtextfields values are amended update the jtree then update the xml document.

Hope i made myself clear.

Example

<cardb>
<car id="1">
<carmake>Ford</carmake>
<carmodel>Ka</carmodel>
<enginesize>1.2</enginesize>
</car>
<car id="2">
<carmake>Porsche</carmake>
<carmodel>GTI</carmodel>
<enginesize>3.6</enginesize>
</car>
</cardb>

JTree structure would look like;
<1>-Ford,Ka,1.2
<2>-Porsche,GTI,3.6

so you select 2 from the tree and click on it;

the JtextFields carmake=Porsche, carmodel=GTI, enginesize=3.6

now you change the enginesize=4 and click a button to update;

thus the JtextFields now equal carmake=Porsche, carmodel=GTI, enginesize=4

JTree structure would look like;
<1>-Ford,Ka,1.2
<2>-Porsche,GTI,4

and the xmldata source would look like

<cardb>
<car id="1">
<carmake>Ford</carmake>
<carmodel>Ka</carmodel>
<enginesize>1.2</enginesize>
</car>
<car id="2">
<carmake>Porsche</carmake>
<carmodel>GTI</carmodel>
<enginesize>4/enginesize>
</car>
</cardb>

Can anyone create this small example of manipulating a xml data sorce using these components?  I need it to minipulate myself for a customer db stored in xml.  As this is a difficult question and time consuming I will give 2000 points to any one that can give me a example class.

Cheers in advance

Pete