My old cattle dog was diagnosed last October. I was a complete failure at doing the blood testing, so we've been rolling on without it. Up until recently he's been doing very well with a reasonably controlled diet and twice daily injections. The injections are very easy - the needles are very fine and my dog doesn't feel them unless I've been clumsy.
I suspect he now has another issue going on, not, I don't think, related to his diabetes.
It's a bit of a shift in managing him and restrictive because he needs the injections at roughly the same time every day. But with careful management, diabetic dogs can have excellent quality of life and a normal life span.
There are a couple of Facebook groups for people managing dogs with diabetes and they are a wonderful source of information. They can be a bit dogmatic (sorry), in presentation, but the quality of information is invaluable. You'll turn them up with a search for canine diabetes.
It's not a cheap disease to manage, but my dog uses human insulin, which I buy from the pharmacy (with a prescription from my vet), which has eased the financial burden somewhat.
It's worth making sure you have a vet with experience of the disease - not all do.
There's a very high chance your dog will go blind as an effect of diabetes, so that's something to hear in mind. My dog has about 15% sight now, but he manages pretty well.