Find Guid in String 
$guidPattern = "(\{){0,1}[0-9a-fA-F]{8}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{12}(\}){0,1}"
[Regex]::Matches($string, $guidPattern).Value
Details
Uses regex to return a Guid inside of a string.

Example
PS C:\> $string = 'Find the guid 1d10da0a-88b2-4129-93a1-e4e33edb3cc5 in this string.'
>> $guidPattern = "(\{){0,1}[0-9a-fA-F]{8}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{12}(\}){0,1}"
>> [Regex]::Matches($string, $guidPattern).Value

1d10da0a-88b2-4129-93a1-e4e33edb3cc5
  |  
Generate a Guid 
[guid]::NewGUID()
Details
Generate a new Guid

Example
PS C:\> [guid]::NewGUID()


Guid
----
19587ae6-b148-4258-89fa-09e240afeb69