Diagnosing- to do or not to do?

Hello all,
Recently my 2012 Prius has been experiencing some brake issues. Yesterday, three lights on my dash displayed, the traction control light, abs, and (!) light. I noticed that the regenerative braking doesn't work and my brakes don't have nearly the same stopping power as before. And there's the electrical whirring present, which happens every 30 seconds or so. Took it to NAPA, and the code c1391 popped up. I've dug around the forums here, and I'm certain it's an actuator-related issue. I've called around different mechanics, and they've all told me to get a diagnosis. It's about 160 to get it diagnosed, but I'm unsure if it's worth it. I'm approaching this issue on a tight budget and am not sure if it's worth diagnosing if all the signs are pointing toward the actuator and booster being replaced. What do you guys think, is it worthwhile getting the diag, is it possible that it's the actuator but maybe the booster is fine? Any advice is appreciated, thanks!