Do the changes to

Officer

Royal Guards

Saboteurs

apply to campaign and skirmish games or only to skirmish games?

(sorry if that was answered before)

The errata applies to both campaign and skirmish, but the change to the Order ability of the Officer does not affect the campaign due to its wording.

You may want to house-rule to use the old Rebel Saboteurs in the campaign mission Target of Opportunity.

Is there a way to get updated cards or how do you keep track of these changes?

Printing out the pdf FFG provides and sleeves.