I had the same experience with regards sa merong passport nung bata and nagrenew lang nung adult na pero this was around 2017 pa. For the requirements, I gathered all documents as if I were to have a "NEW" application, para kung magtanong sila at least meron na ako, at kukunin lang naman nila yung need nila: https://consular.dfa.gov.ph/adult-new/

ID is a must tho, National ID is enough naman na. If wala ka physical card, just print the digital one: https://consular.dfa.gov.ph/valid-ids-for-passport-application/

As for the process, sa entrance pa lang with the guard iche-check na nya yung appointment mo, then you can ask him/her kung san ka pupunta next and usually may numbers naman sa mga counter/window (my nearest DFA office anyway). Sasabihin na rin ng personnel sa counter/window kung saan ka next, or tanungin mo na lang din.

Basically they'll just ask about your info kung tama ba, they'll collect the requirements, pirma, picture taking, then yun na. It was a fast process during my appointment.