Diabetic 80lb dog.?

My husky/shepard mix was dx with diabeties last week. I have been all over the net searching for some answers. Here is the basic gist. I'v struggled to get this dog to an ideal weight her whole life (8 1/2 years). The last couple weeks I have noticed that she just can not go very far on her walks. She would get about 3 or 4 houses and she would lie down. At first I thought her toe nails were too long and I cut them. Then I tought she was artheric(not uncommon in a shepard) about a week or two later she seemed to be losing her vision, and the back legs were getting worse. I also noticed that she was not shedding like she should (she thorws her coat twice a year). I thought that this was a sign of old age, but I was super concerned about her legs. I took her to the vet and was told the news. I was sent home with vetsulin (18u) twice a day and a diet high in fiber the vet reccommended wd. The good news is she can walk with no trouble. I am out of room I will post my questions next.