1. Don't do this! The ticket reissue is going to be extremely time consuming-- you definitely need to call the RTW desk first and get everything changed. Even then, it will be time consuming getting the new ticket printed.

2. Sounds like a major hassle rescheduling your entire trip-- if it were me, I'd just cut my visit to EZE short and chalk it up to experience. Other than that, my understanding is that the fare now allows you to transit LAX when you are proceeding directly from HKG to EZE (this used to be prohibited).