lisa,
DO NOT cancel your trip because of stories you've read about, comments from co-workers or whatever. Roberto (who is originally from Italy) provided an excellent perspective. While there is certainly cause for concern, if you take a few reasonable precautions (Money Belt, situational awareness) and present a confident demeanor, you shouldn't have any problems. I wouldn't suggest keeping your train tickets in your Money Belt, as you'll need to access it to present tickets to officials. Money Belts should not be accessed where others can see!
Although Milano Centrale has a bit of a "reputation", I've never had any problems there, although there are a couple of things to be aware of...
- Watch your bags at all times. Is there some way you can clip your two bags together when you're not holding them? That will discourage opportunistic theft to some point. Your PacSafe pack will be lockable, so that will provide some security.
- The WC's are one floor down from track level along a moving sidewalk. You will need Euro change to access those as they use a coin-operated gate to control access.
- You may be approached by well dressed people soliciting "donations". How you handle that is your choice but I rarely give them anything.
- When you board the train, you may find small cards with a "hard luck story" (usually in Italian) asking for donations. Just prior to departure, a teenager will come through and collect the cards and have his hand out. I usually tell them to "take a hike" but be prepared as some of them can be quite forceful and persistent.
Note that if you pre-purchase tickets for the Intercity or Freccia trains, these have compulsory reservations which are specific to a particular train, date and departure time. You MUST ensure that you board ONLY the train specified on your ticket or you'll face hefty fines which will be collected on the spot! If you're riding Regionale trains, you MUST validate the tickets prior to boarding the train on the day of travel, or again hefty fines.
Regarding cash for use in Italy, I'd suggest either getting €50 or so from your Bank before heading to Europe or stopping at a Currency Excange office in Lugano (might be one at the station - I can't recall). Currency Exchange offices typically provide terrible conversion rates but for a small amount (even €20) that won't be significant. When you arrive at Milano Centrale, buy a coffee or something, and that will provide some coins for the WC.
I rarely buy first class tickets, as second class is perfectly comfortable. While on the train, you should be able to place your PacSafe backpack in the rack over your seat, and keep your carry-on either on the floor or on the seat next to you if no one is sitting there. There are luggage racks at one end of each train car for larger items, but I prefer to keep my bags with me whenever possible.
Which of the five towns in the Cinque Terre will you be staying in? When you see the area, you may wish you had booked more time there.
When you return to Milan, you may not have to stay close to the airport, depending on what time your flight departs. Travel time to MXP is only about an hour so you may be able to stay in Milan for the last night.
BTW, I'm 60+ and routinely travel solo in Italy without any problems (so far).
Hope you have a wonderful trip!