Tim posted a link to my Trip report above. We were there last April and our primary focus was Pompeii and the other Vesuvius related sites. It depends on your level of interest but the typical 2 hour tour that gets recommended on a lot of sites would have barely scratched the surface of the history of the region. We took a deep dive and spent about 12 hours over two days at Pompeii, plus another two hours at the Villa of Oplontis which is one train stop north of Pompeii. I highly recommend that if you have time. We also spent a day at Herculaneum and several hours of another day at the Archeological Museum in Naples to tie it all altogether.
Naples is also worth a full day and not just for the museum. It is a city unlike any other I've ever been to. It's dirty, grimy, crowded, but a gem to experience.
We enjoyed Capri considerably more than the Amalfi Coast and aside from looking at Positano from above and then from below it is unimpressive and we were ready to move on. Capri is easy and quick to get to by ferry and has views just as spectacular as anything you'll see on the Amalfi Coast. People complain about how crowded Capri is but I suspect there are some who don't plan and go straight to the main street in Capri Town and venture no further. The Rick Steves guide about tackling Capri is very beneficial to beating the crowds.
We did spent two days doing day trips on the Amalfi Coast. Be warned that transportation is chaotic, confusing and unreliable and you'll spent much of your time getting from place to place. We did a 9 hour tour through Mondo Tours and 4.5 of those hours were in a vehicle.