Good to hear that the diabetic nurse was good. Some of the reason for being diabetic is genetic, and you can't do anything about that, but you can, as you say address diet.
I would say, start slow and look at what you like to eat, and see if you can change a thing or two in some of your meals to reduce the amount of carbohydrate that you're eating. It's the carbs that'll put your blood glucose up, if you reduce some of that, it'll make a difference, but you don't need to do it all at once. The metformin will make some difference, but it's not a magic bullet, sadly.
So maybe look at a meal and think what you can change, so swap cornflakes or toast for omelette with bacon and mushrooms (if you eat these). Or instead of a sandwich at lunch, have a bowl of soup and an apple. Or make lower carb bread, and slice that and put it in the freezer and have it instead of regular bread. There's a video on youtube called something like: Diedre's low carb bread which looks a good recipe.
It's easier if you also buy a blood glucose monitor, and you can see what each meal does to your BG, by testing before and 2 hours after each meal, but you don't need to do that on day one.
I can recommend buying a copy of
Carbs and cals, so you can see what each food has in it.
I know it's a bit restrictive compared to what you had before, but you can do something about the path that your diabetes takes, if you keep your blood glucose controlled, you may be able to reduce the medication, and minimise the risk of any complications.
Ask away with any questions you have. I've found this a lovely community, really helpful.
It does get easier, honestly, regards, Sarah