PF30 cup came out of frame, can it be pressed back in or should it be replaced?
Once you get the bearing and cup off the spindle, you can assess the state of the bearings a little. Turn them with your fingers while pushing hard in both the radial and lateral directions. This kind of test isn't perfect because the loads applied in use are so much higher, but sometimes it can reveal notchiness or roughness that lets you know you'd be better off replacing them.

Unfortunately, between the creak and the ejection of the cup, it's likely that the bore on the frame is either oversize, roundness-challenged, or both. You could check it with calipers if you want. Any such issues can have an adverse effect on bearing life, as the creak indicates the cup is moving a little which in turn means the bearing alignment won't be ideal. If there's no or minimal wear or roughness detectable, on a personal bike I think it's fine to just re-use it and see what life one can get out of it. While it's convenient I would lift the bearing seal and degrease and re-lubricate it, but that's optional. One nice thing about doing that is once you get it clean and re-check how it feels, you can get a better read on whether any roughness or notchiness was caused by contamination versus damage to the races.

On the other hand, it wouldn't take much perceptible wear for me to just replace it while it's out.

Retaining compound is a good idea and hopefully it will eliminate the creak.