Groundspeak don't actually ship the GUI ID for a cache in the GPX file per se.
However, it is contained in the URL . So as a work around to pull out the GUID you could use the %macro tag in your custom URL if you really needed it.
As for the WptTypeID, I personally don't know as it is a Groundspeak item. Some other GSAK user might be able to help you out on this one, or you may have to ask your question again in a more Groundspeak specific thread.
I have the same question.
I like to access this page (http://www.geocaching.com/seek/gallery.aspx?guid=<the cache guid>) via custom URL in GSAK to get all the images for the selected cache.
Therefor I need the GUID.
How do I extract it from the url?
Best regards,
Mikael Klingbjer - TeamGoonies