i'm 1/4 native american (tsalagi/cherokee), and all the relatives on that side of the family have had adult onset diabetes.
i was diagnosed when i was a skinny little jock (well, not skinny but mostly muscles and little fat) -- so i'm confident that in my case it was all about genetics, not lifestyle. my diet's always been right on, too.
i have a disorder called RSDS, basically nerve damage that wreaks all sorts of havoc with the body kind of like neuropathy can. the RSDS is what makes my legs swell up, ulcerate, makes me feet numb, etc. -- but because i'm diabetic, wounds don't heal quickly at all. so when i get an ulcer on my leg, i have to be very very careful not to let it get infected; that's how stuff like amputations come about. it's not the diabetes per se that makes it necessary; it's secondary things like wounds getting infected.
also, since i can't do diddly for exercise much of the time, i've been putting on weight. i still eat right and follow the diabetes diet guidelines (which are very good, and i do NOT feel like i'm deprived or anything), but we're big, beefy muscly guys in my family, and if we don't burn calories, we put on the chunk quickly. and that sucks, because the more fat you have, the less insulin is processed normally, etc. -- kind of a vicious cycle!
anyway, diabetes IS manageable far better now than ever thought possible. the medicine is much improved, and not every diabetic is now "doomed" to a life of needle sticks. my big health concern is the RSDS. my other family members with diabetes have lived with it very well for decades. at 38, and even with everything else going on healthwise, i still just take an oral med for the diabetes (glucatrol extended release).
anyway, if i could offer any advice, it would be this --
CHECK that blood sugar. only when you know where it's at can you adjust any medication/diet appropriately.
give up any sugar that you can. while it's counted as "just another carb" now, and while diabetics can and do eat and drink things containing sugar, the less of it you have, the better things go.
keep sugar-containing snacks around at all times. when one's blood sugar crashes, it's necessary to bring it up asap. if you can eat a meal, that's ideal. if not, have some lifesavers around.
exercise. can't say enough just how exercise benefits diabetics particularly. it helps get or keep weight down, and it helps out in regulating blood sugar.
take care of your FEET! if someone develops neuropathy, you can't feel it if you have a blister or a cut on your foot. people don't generally examine their feet daily, so a diabetic w/ neuropathy can have a raw spot, blister, cut, etc. that they don't even know is there -- that can get infected and turn gangrenous, and that's what causes limbs to be lost.
yes, it's scary. very scary... especially when someone is newly diagnosed. but MOST complications of diabetes are PREVENTABLE! and that is very, very good news! i am VERY much the exception to the rule here. again, diabetes plays a part in my health issues, yes, but it is a SMALL part of things.
read up, get educated, see a nutritionist if need be, and just live life for all it's worth -- and that's a lot. hang in there!