I have been mixing D-76 for a few years with complete success. You can get chemicals from photographer's formulary and the supermarket. Just one suggestion, if you use the developer right away, you can use the original formula but if you want to store it for a while (up to one year) use the buffered formula with boric acid in it. The original formula changes activity with storage time, believe it or not, it gets more active with time and your contrast will come out too high. I use the buffered formula from Anchell's book. Dissolving boric acid is slow, but I use a stirring hot plate which removes most of the pain of dissolving powders. Some say the D-76 you buy today is actually the buffered version, but I don't know. Good luck and have fun.

Best regards,
Chris