Read xml file and lookup data in csv

Hello,

I have two files, one xml and one csv file.  The .csv file has two columns, the first column containing the value from the xml and the second column containing a value needed to update the .xml.  The ask - to read the xml file for the specific value, compare that value to the data in the first column of the csv file.  If there is a match, take the value in column B and update the .xml.  If no match, update the xml with a generic value.  The csv file is comma delimited.    There could be multiple xml files in the subdirectories that need to be read.

Example files attached.  

The XML - <testdata TestDataToLookup="test2" random="data" TestDataToInsertFromCSV="" random="data"/>

test2 would be looked up in the csv file and column 2 would be inserted in between "" of TestDataToInsertFromCSV

Assuming the file would start with something like:
$path_search = "c:\test\ReferenceFile.csv"
$path_target = "c:\test\" - there could be multiple xml files in different subdirectories to be scanned.

Get-Content c:\LookupFile.xml

$LookupFile = Import-CSV "C:\ReferenceFile.csv"

Very new to powershell.  Any help in the right direction would be appreciated.

Thank you
test.csv
test.xml