Firstly, congratualtions :0) Sounds like you're really pleased with the news, if a little apprehensive.
I used to work at a diabetic ante natal clinic, so I would say get in touch with whoever has clinical responsibility for managing your diabetes and share your news straight away so you can be brought to the attention of obstetric staff and endocrinoligists.
Pregnancy is a time when lots of women make significant changes to health habits, it looks to me as though that's just what you are planning. Good luck, and let go of the guilty feelings about previous poor control, onwards and upwards :0)