Edmunds says your car gets 21mpg city, 27 highway (21 combined), which isn't great, but it's not that horrible, either, realistically. The scion, in comparison, gets 27/34, 30 combined.
So, if you drive the "standard" 12,000 miles a year, you're burning 571 gallons of gas in the Volvo, or 400 in the Scion. That's a savings of 171 gallons, or about $684/year by switching cars, on gas alone. You also have to consider the cost of insurance, and the purchase price of the car. Also, the Volvo being as old at it is, probably isn't worth more than $3,000 or so, so the value of the car can only drop by so much if you decide to keep it until it dies.
The repair shop being half an hour away seems sort of immaterial, especially since you say it's mostly dependable now. It's a one-hour round trip to get it worked on, what, every few months? How much closer is the shop you'd take a different car to?
Plus the Suzuki seems like a pretty mediocre car. I'd rather drive the Volvo, or the Scion for that matter, but I really wouldn't want the Scion either, despite MRM's love for the thing.
No used car is going to give you perfect peace of mind. A used car has to earn your trust that it won't break down, and it does that by not breaking down on you. Your Volvo is already a known quantity here -- you have expectations about how reliable it's going to be. Any other car you get is going to be starting over, and you hope it doesn't break down the day after you buy it. Sure, a scion will *probably* have less maintenance problems than an older Volvo, but you don't really know for any particular car until you give it a try, by driving it for a while.