Hi Gilligan50
Welcome to the Community! You've picked a great trip for your first JY adventure. I did it in September 2015 and loved it. If you put Pompeii into the search facility on the top right of the page you will find loads of reviews and thoughts from people like me.
My top tips would be take very comfy, closed toed walking shoes because the paved areas at the ruins themselves are very uneven, as is the cinder path up Vesuvius. Also, take a hat, as there is very little shade and drink loads of water. Finally, try the local granita because it's very refreshing in the heat and also, if you like gelato and/or pastries, head for De Vivo - it's a local gelateria and bakery half way between your hotel and the ruins. My group quickly adopted it as our 'local' - it's fab :P
Happy to help if you have any other questions once you've read the reviews
All the best
Mandy