Hi tml,
First of all, welcome to the JY forum and congrats on your booking! I know it can sometimes be scary but remember whilst you are travelling by yourself you will not be alone. There will be others on the trip that are new and a few others that have used JY many times. There are many responses and testimonials on the forum about nervous first timers, so my advice would be to have a read through as you will probably be encouraged.
I am seriously considering this tour on the date you have booked as i will have just finished uni and the tour now contains Herculaneum which, in addition to pompei, capri, sorrento and mount vesuvius, are the destinations in Italy i have most wanted to visit, thus making a marvellous trip. It is remarkably cheap for Italy as well!
I have been to the Cilento Coast, Paris, Croatian Istrian Coast with JY so if you have any questions about them i am all ears.
Thanks
Mark