The 401 error is caused by your Request URI:
Dim Request As HttpWebRequest = WebRequest.Create("http://api.constantcontact.com/ws/customers/tristatehomeservices/contacts")
That should be:
Dim Request As HttpWebRequest = WebRequest.Create("https://api.constantcontact.com/ws/customers/tristatehomeservices/contacts")
Change that and you should be able to get a valid response of 201, 400, 409 or 415 depending on your actual XML content.
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