As an expat in a different situation (DoD expat under the Status of Forces agreement - aka "the easy way") for 8 years I totally support people becoming expats abroad as long as they do so with clear eyes. I only skimmed the many posts here so apologies if some of this has already been addressed, but I wanted to speak more to the emotional as opposed to the practical issues of becoming an expat:
-Learn the language. I don't speak German. I thought I'd be here for one years, then 3, but halfway to 3 is when I started encountering the difficult grammar and gave up because, "What's the point, I won't ever need German again anyway!" I should have just buckled down and finished at least B level classes early on. Even in a place like Germany where many people speak English, it's very hard to be part of any community in a real sense without fluency in the language.
-Live someplace with an expat community. Even if you speak the language, it can take years for locals to really accept you, so for not feeling isolated, an expat community will provide you with the social fabric and just a ranting/sounding board. Within an expat community, it's VERY helpful to befriend mixed-nationality couples - i.e. a local and their foreign spouse. It's a great "bridge" between the two worlds.
-But also understand that expat communities can full of toxic people. Some expats really are "running away" from something. There can be a lot of drama. It varies from place to place but a lot of expat communities can be insular, incestuous, and difficult to find a foothold in. Don't be discouraged. It took me about a year to find people I'd really call friends here, and a lot of trial and error.
-Since you lived in Italy for some time, you probably already know this, but real life isn't a vacation. Even if it's retirement. The shine can wear of quickly, especially if you've tied yourself to a place and you don't have any plans to move back to the states. Living abroad can be a very lonely, isolating experience, and homesickness is a thing. For me the best cure is to remind myself why I love living here in the first place, whether it's going to a unique local festival or taking advantage of travel opportunities.
-Don't lose touch with friends and family back home. With social media it's easier than ever to stay in touch, but it's also easy to mistake reading Facebook with real social interaction, even from afar. Make the video calls, write the emails, etc. This is something I was better at when I first moved away, and am trying to get back into doing. One of the loneliest feelings is returning to your "home" for a visit and realizing life goes on without you, even while you may not feel fully rooted to your new home, either. It's a paradox, but becoming an expat grants you the gift of two "homes" while often making you feel somewhat homeless at the same time. Spend enough time away and you will feel like a foreigner in your home country, but it's very difficult to feel native in your new country. That's the tradeoff for all the amazing benefits of living abroad.
8 years in, I wouldn't change this experience for anything. I have friends all over Europe, I live a great life, I travel frequently, etc. I also miss my home, miss how things "work" at home, miss my friends and family back there. I'm supposed to return to the States soon but I'm now at the point that I hope to eventually live abroad permanently, but it's important to be honest about the pros and cons of choosing this life! Good luck to you and I hope you're able to realize your dream!