Get and Set XML elements with Namespaces

NEWBIE QUESTION. Hi, haven't worked that much with xml, nothing like this anyway. I have some xml as shown below that I receive which has several Namespaces. The idea is I read some values, then update others before returning the revised xml with Namespaces intact -don't want them removed.

I am given the path to some of the elements like this "cred/sub/aa" or "trip/items/item[0]/customerInfo/custName". But it seems that namespaces make it difficult to get to those elements so simply.

Does anybody know how I can read some of the values like "NON-SMOKING" from custPref or get the value "CABBAGE" from bossman/zz. Also, I want to be able to then set a value such as custName to say "Mr.X".

Any ideas? Thanks.

<?xml version="1.0" encoding="utf-16" ?> 
<A1 xmlns:xsi="http://ift.tt/ra1lAU" xmlns:xsd="http://ift.tt/tphNwY">
    <cred xmlns="http://ift.tt/1vajMbf">
        <sub>
            <aa>Zippo</aa> 
            <bb>lighter</bb> 
        </sub>
        <reqId>
            <cc></cc> 
            <dateOfBirth></dateOfBirth> 
        </reqId>
    </cred>
    <reqName xmlns="http://blah-blah/vader/base">qwerty</reqName> 
    <reqId xmlns="http://blah-blah/vader/base">12345</reqId> 
    <machine xmlns="http://blah-blah/vader/base">
        <qqq>hello</qqq> 
        <www>goodbye</www> 
        <eee>99999</eee> 
        <rrr>88888</rrr> 
    </machine>
    <monkey xmlns="http://blah-blah/vader/base">alskdjfhg</monkey> 
    <math xmlns="http://blah-blah/vader/base">
        <language></language> 
    </math>
    <trip xmlns="http://blah-blah/simple">
        <tripOverview xmlns="http://blah-blah/vader/base">
            <description></description> 
            <cost></cost> 
        </tripOverview>
        <bossman xmlns="http://blah-blah/vader/base">
            <zz>CABBAGE</zz> 
            <yy>BANANA</yy> 
            <xx>MELON</xx> 
            <ww>SYRUP</ww> 
        </bossman>
        <items>
            <item>
                <itemSummary xmlns="http://blah-blah/vader/base">
                    <description></description> 
                    <cost></cost> 
                    <reference></reference> 
                </itemSummary>
                <customerInfo xmlns="http://blah-blah/vader/base">
                    <custName></custName> 
                    <custPref>NON-SMOKING</custPref>
                </customerInfo>
                <seatId xmlns="http://blah-blah/vader/base">1</seatId> 
            </item>
        </items>
    </trip>
  </A1>