Pulling My hair out!!!

Well we can't change geography! You could pay for a private driver, but that is still a long time in a car and expensive. Are you planning on any other day trips from Sorrento? You could pick a different base. The towns along the Amalfi Coast close to the mainland, or even Salerno, would place you more centrally located to reach Paestum and still allow for day trips to Positano, etc. Alternatively you could overnight in two places if you have enough days to work with.

Best to spend a night or two in Paestum and/or Salerno.

Instead of pulling your hair out, why not just adapt your travel plans and not stay in a single location as the base?

We are booked at this place in Sorrento and I've already paid up front :-(. What you suggest is probably the way to go but I'm kind of locked in.

We faced the same dilemma a couple of years ago. We settled for going on a tour with Golden Tours. The price was reasonable - -I'm remembering 40 euros/pp - - and the guide was good. Of course we had to sacrifice flexibility. We would have preferred more time in Paestum, but we did get to see it and Salerno hassle-free.
Just for your information, I think seeing the 3 AC towns in one day is too much. Amalfi and Ravello are way more interesting than Positano. The latter is mostly shops catering to affluent tourists.

Thanks for the tips. I guess instead of going to Positano first we can head to Amalfi and Ravello . Work our way back. toward Positano then back to Sorrento

I've already paid up front

Lesson learned - better to hold off paying upfront for lodging until you are very comfortable with your schedule plus the tradeoffs from tying yourself to a single base (hopefully the money you save from an advance booking is a net benefit for a loss of flexibility). Good luck! You may have some long travel days ahead but at least they will surely be fun-filled.

If you can choose more time in Paestum and skip Salerno, I suggest doing so--especially if you have not seen Greek temples before. It was a major highlight of my visit, and the museum is very impressive as well.
Agree about Positano, Amalfi, and Ravello pushing it for one day, but if you are early risers and the bus/ferry cooperates go for it.

We did Paestum a few weeks ago from Sorrento, day trip with Monetti taxi. It was so worth it, 350 euro. We are a family of 4 and we limited our number of apartments to 4 during our 3 week trip to Italy. We also did a boat tour from Sorrento to Positano and Amalfi, gorgeous views from the water and swimming and about 2 hours in each stop, thoroughly enjoyed. Sorrento was the place we spent the majority of our tour money, worth it to see what we did.

I suppose we could take the train to Pompeii from Sorrento and go straight to Paestrum and bypass Salerno. Would be easier. Really wanted to see if we could take a ferry back and view the coast line. Think the train to Pompeii is about half hour and train to Paestrum is about an hour.

You will need to change from the Circumvesuviana commuter train (Sorrento-Naples) to the Trenitalia train to get to Paestum. The stations are about 15-20 minutes walk apart in Pompeii. Be sure to buy round trip tickets to Paestum, as there is no manned booth at the Paestum station.
If there is a Salerno-Sorrento ferry, you could go from Paestum to Salerno and take the ferry.

" Hate to spend most of the trip traveling for just a few hours of viewing."

that's the core problem with day trips.

It's about three hours each way from Sorrento to Paestum, whether you go back to Napoli Centrale-fast train to Salerno-bus to Paestum, or go through Amalfi to Salerno to Paestum.

Whether that much travel time is worth it to you, I don't know. I would spend one night in Paestum (keep the room in Sorrento), then go back to Sorrento via Amalfi/Ravello and Positano the next day.

Zoe makes a great point - if you just accept that you will double pay for one night (a room in Salerno or Paestum in addition to your pre-booked room in Sorrento), you'll have a much better time than trying to do all this in one day.

Paul, in 2014 I had a great day trip by train from Naples to Salerno (about 2-hour visit) and on to Paestum for most of the day. Thus was plenty of time to go through the wonderful Greek and less wonderful Roman ruins, and visit the very nice relatively small museum right by the ruins. Had both breakfast and dinner in Naples.

Zoe and Harold make a good point. I think if we leave early enough and spend maybe 3-5 hours in Paestrum,catch the train back about 18:00 we should be back in a reasonable time.Plus ,we kind of left the next day open so we can sleep late and kind of decide what we want to do if anything

if you are searching things in the web of the internet, note that there is no "R" in Paestum. It may make it easier for you.