Upgrading from PE to UC?

Hi there,
I've been looking into upgrading on my return journey from LAX to Upper Class, I'm currently booked in Economy (outbound) and PE (s fare) inbound, Now I've looked on the website and it seems if I enter upper class for the return I get a price of 1067 which is about 210 extra which doesn't seem to bad, is it that simple that they would calculate it like this (+ I'm guessing a change fee?) and do you think calling reservations of Frequent Flyer would be more beneficial?
Thank you in advance
I've been looking into upgrading on my return journey from LAX to Upper Class, I'm currently booked in Economy (outbound) and PE (s fare) inbound, Now I've looked on the website and it seems if I enter upper class for the return I get a price of 1067 which is about 210 extra which doesn't seem to bad, is it that simple that they would calculate it like this (+ I'm guessing a change fee?) and do you think calling reservations of Frequent Flyer would be more beneficial?
Thank you in advance