Originally Posted by
findark
Changing the ticket will always revalidate all of it.
Your new itinerary violates the 7-day minimum stay provision of the original fare. Using fares in effect at ticketing, this would reprice to PHX80NPJ outbound (USD 1380.00 add/collect) and AHX70NP1 (USD 245.00 add/collect). In theory the GUC should need to re-clear, and not sure if there is space (Z0 alone, Z3 married from PDX).
Sometimes you can change for free after the outbound portion has been flown. This requires meeting minimum stay, day of week, etc. restrictions in the fare and also needs fare class availability on the new flight(s).