I've only had mine for a bit under a year, but so far I have serviced it entirely myself and haven't had any big issues (to be fair, I picked up a well-looked-after example). The biggest issue I had was replacing the harmonic balancer and pinning the crankshaft. A real PITA job, but still DIY-able. This forum and YouTube are great resources for learning about this car and it is a heck of a lot more DIY friendly than anything modern. At the end of the day, it's just a regular car with a big@$$ engine and you'll get more thumbs ups than all those self-absorbed folks with their modern bling. None of that new stuff resonates with our primal instincts quite like this car. On good days (dry, warm), I'll commute to work with it and merging onto the highway with free space ahead of you is always a blast.
I've spent a few grand on tools and additional parts to make the car a bit more reliable (more like trying to get ahead of potential problems before they show up). I plan to keep investing in tooling for DIY work on this car. The irony is that I live not too far from Tator's Garage and, although I know they have god-like status in the Viper community, I'd rather do the work myself if I can (saves on labor costs, I learn stuff, and I can do it on my own schedule in my own house). I'll lean on them if I absolutely need to (e.g., mounting tires), but otherwise this car has motivated me to learn how to do more of my own car work. I think as long as it's nothing super serious, like an engine pull/rebuild, then you can do most of the maintenance yourself with the right tools and a bit of research.
If you don't want to do any of the maintenance yourself, then just be prepared to spend more and also make sure you find a trustworthy Viper tech in your area. In some areas, that's simply not possibe and so you have to man up and do it yourself. As long as you have a good example, then your costs should not be high as you're just dealing with consumables (oil, brakes, tires, etc.).