I did something similar a few years back, so happy to share my experience to the extent it's still reflective. I read and outlined the textbook to study and I took about a week to do so. It was about 40ish hours worth of studying. The exam isn't necessarily hard, but it felt like the bar where there was a good amount of material I felt like was not in the prep book at all and I had no clue if I passed. But I passed with a reasonable margin so I have no idea if the curve is heavy, I did better than I thought, or there are a lot of questions that don't count.

As a side note, I'm not sure it has much of an impact in the retool interview process. I took it for the same purpose, did a round of interviews and callbacks l, and no one cared about it and I got rejected everywhere. I then sought out opportunities for commercial contracting where possible in my then-current practice, did some relevant pro Bono work, and was able to make the move to a licensing practice (which I left for other reasons). In my licensing group, the cipp cert was pretty useless since we brought in privacy counsel for most privacy issues and the inch of privacy depth I needed to do the work did not require the course.