If you're going to use any injectable gear, then of course you're going to need some "darts." You can pick up syringes at your local pharmacy unless your state has certain restrictions. Also, you can purchase needles online. Just do a little searching around and you'll find several places that'll hook you up. Syringes will run you around 50 cents apiece. Note that it'll be more difficult to obtain needles (at least from the larger, more "legit" companies) if you live in California and Illinois. You'll usually need a doctor's prescription in those states. Still, if you look around enough, you can get what you need.
Taking any form of Steroid if you are diabetic is never a good thing as it makes controlling diabetes B/G levels very much harder due to the inevitable rise in B/G levels. Steroids causes an impact in the body basal metabolism, which makes diabetic patients a susceptible target to that impact increasing or moving the lipid profile and glucose levels to the roof is not regularly control and checked. The short term complications can vary and be very simple(or not) long term complications are a big problem here (macro and micro-vascular complications). Can you use them? maybe… but at the end is your decision. Never do anything without consulting your physician.