does PACU, OR, ER, ICU, NICU, PICU, CCU pay more?

Both.

Some places pay more,and some don't.

In order to work at my ICU, I had to have ACLS, and a documented criticial care course (or experience as a ICU RN already)

Both the ACLS, and the critical care course were paid for and provided by my work.

Orientation typically lasts 4-6 months for critical care areas.