recommended training prior to tracing

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I am having a problem with getting a token from Google Oauth2 on my linux PC. The request for a token is coming from a an extension running in a copy of Chrome. I have fooled with Wireshark (and Ethereal before that) long enough to know I don't know $%$%^ about using using it. I have two questions:

1. what parts of Wireshark should I concentrate on learning to solve this Oauth issue?
2. What can I read that will get me up to speed on those Wireshark features?

Thx