A few notes to draw perhaps no truly helpful conclusion:
1. The online Fiat enthusiast world will completely spoil you for any other one. I started via the old Italian Car Digest (remember mailing lists, anyone?), then Mirafiori & more recently here. In the interim, I've been part of groups focused on Mercedes, BMW, VW, Hyundai, Honda, Nissan D21 trucks, even Ford trucks (basically, pretty much any vehicle that a family member has owned) and I concur that if Carl DID even get any helpful information about his door locks, it would be after hearing multiple comments to use Google, to search the forum or that generally he was not doing something right (but never offering any of the off-the-top-of-the-head knowledge that I KNOW anyone who's into VWs for the long haul has a lot of.
2. My experience, starting in college when I opted for 2 "interesting" cars vs. one practical one is that the cars confer with one another over night & try to time breakages in a way to leave you often stranded or frustrated. It's not the end of the world, but I'd throw expecting to always be able to commute in your old car (or multiples) off the list of expectations & instead appreciate the days when you can. Don't worry, those days of appreciation will be the norm, but every so often, something little comes up & life/weather/timing/budget may leave the car parked for a day or two.
3. For about a decade or so of my Fiat enthusiast experience, I had a work-issued vehicle to use to commute & any trip that was attached to the commute (ie, errands, stop at the grocery, kid logistics, etc.). That allowed me to indulge in owning cars for which I did not have to worry about any being operable on any given day. This was a blessing & a curse. It was probably convenient early on when my family & hobby operating budgets were small. Later, it became a burden to be able to put ENOUGH miles on the Fiats to keep them healthy. For the last 8 or so years, I've not had the work commuter car and ultimately, that's been a great thing for me. (not so great for folks who work for me who also no longer have this & it represents a larger % of operating costs for them & they don't have 8-9 cars at home...a couple actually had to buy commuter beaters when the change went down.)
4. Fiats are rather easy to work on and in my experience (hope I don't seriously jinx myself) pretty reliable once they are sorted & if you give them the level of care & routine maintenance/inspection pretty much any car of their era should get. Tools help. I started about 30 years ago with the philosophy of buying the right tools (including reference materials) to do jobs correctly. Coming from a zero base knowledge childhood, that meant that early on I had to do a few jobs twice to get them right. Still, it was cheaper than hiring out and afterwards I had an increased knowledge base and the tools. Two factors that help there are that I usually enjoy working on cars - it's almost therapeutic. Also, I'm an engineer, so I probably have an orientation to mechanical things that's helpful. I've taken both those for granted and found myself confused when trying to help car enthusiast friends who seem utterly overwhelmed...so, I always recommend knowing yourself & what you WANT to do. If you don't want to do the work yourself & sometimes have your social plans changed because you need to fix something, but you still want to own a classic Fiat & rely on it as a daily, then plan on having a lot of money to pay someone. (multiple cars help here...modern beater or whatever).
5. While I agree that some cars are quite special & perhaps are best suited for fair weather use only, these are also relatively inexpensive (and quite CHEAP compared to the enjoyment factor) cars. If you maintain the car and take reasonable precautions to prevent rust, I'd say not only is driving your car regularly not bad for your car, it's GOOD for it. Your car will almost certainly be in better running condition than any of the beautiful trailer/garage queen cars, and for me THAT (and the inherent experience of actually enjoying vs. encapsulating it) is what it's all about.
6. I went through a similar thing with my own "fleet" over the last few years. While i've always owned multiple Fiats, I had actually sold off a few, along with my niche E28 535is BMW & bought a new VW TDi Sportwagen in 2014. The TDi was sort of my non-Fiat dream car that I'd wanted since long before that model even existed & this one was special ordered with some nice wheels, all the options & a 6 speed MT. Then a couple years & about 40K miles into the weird world of owning a "new" car that was under warranty, the whole EPA/VW scandal broke & the short story is that VW bought my car back and I got something like 99% of my money back. I thought I might NOT replace it with another newish car and instead drive my Fiats (augmented in theory by getting Carl's cool 128 wagon). In the process I also "sold" my very nice '71 124 Spider via Ebay. Through an odd series of events, that Spider came back to me, a 124 Coupe that I had sold locally came back to me & I ended up acquiring two slightly derelict X1/9s locally. The end analysis on my part was that I probably just needed to actually *drive* the cars regularly. In particular, the thought of selling a super-nice Pininfarina bodied sports car for the same amount some dumb parent in my neighborhood had spent on a 2 seater ATV their kids were driving around the neighborhood at midnight one night really hit me....why not put another 100K miles on the car and then maybe after that I'll sell it for whatever the market value is, which will probably be more than I was going to sell it for today! Anyway, along w/ my "official daily" 1995 F150 w/ 224K miles, I have a whole bunch of Fiats that I can drive with semi-regularity and use as they were originally intended - as cars.
I'd say after thinking about the kind of involvement/experience you want out of the car, if you're still in, go for it! I tend to opt for my F150 at times like the last few weeks when the local highway departments are dousing the roads with salt & brine, but that's not going to be an issue for you. Have fun & good luck!