The deal with Guam at CAL is that there is a 1200 a month Cost of Living allowance out on the island, you get that regardless...
The 2nd year pay and instant health insurance come into play only if you agree to stay out there for 18 months. Since I was hired in April no one has gone out there.
Be advised they will ask you in the interview if you are willing to go out to Guam... A "NO" answer is most likely a deal breaker. Things could change and they could send people out there so be prepared, but right now 70% of the people have been getting EWR and the rest have been going down to IAH.