Hi mymammoth (I love mammoth too!) from a fellow LA solo traveler. All the above advice is great. I've been traveling for 20 years now as a solo and it was a bit intimidating the first time, but you'll do great. My little piece of advice to add to the above is to go to your bank and order some euros in advance. I know a lot of people pooh-pooh this, but I like to have a bit of the currency before I arrive so I don't have to look for an ATM when I'm tired on arrival. I get mine from Wells Fargo and ask for small bills. I just get $200. Who cares what the rate I'm getting for those euros! If you use the wrong kind of ATM in Europe, you get big fees anyway. Peace of mind! (And if you don't use them all, you have them for arrival on your next trip!)
And yes! use your money belt. Who cares if it makes your tummy a little lumpier. I don't think you're looking to get picked up anyway! Lots of people don't, but I carry my passport and credit cards in my moneybelt all the time.
Also, when using your credit card (and I now tap to pay with my phone almost all the time vs cash) DO NOT pick USD as your payment. Always pick euros! (Or whatever the local currency is in other countries). Another way they add fees you don't need. If you need any euro coins for the toilet or such, just buy a water or something to get those.
I love to take a food tour the first full day I'm in a city before my tour starts, it gets me in the mood and I always learn a lot and eat yummy local food. I just looked and Secret Food Tours has a food tour there. You can PM me for a discount code that may work for them.
Lastly, get a leash for your phone. You don't want to have to worry about getting it snatched or leaving it somewhere or dropping it. I'm so glad you're taking the leap - it is very addictive to travel. I'm sure it'll help your grieving heart.