Just wondering which letter this is? Is it your HRT letter? I only ask because where I live, there are at least two different letters that could constitute a "diagnosis" (I agree with your disdain for that term, however...). The HRT letter can come from a psychotherapist, psychologist or psychiatrist. Alternately (or in conjunction), one can go see the Gender Identity Clinic in Toronto (CAMH, which requires a medical referral), and get a "letter" from them confirming "you meet the criteria" (with lots of suitable CYA language for good measure). I've had my HRT letter since the end of November, and finally have an appointment with an endo for the 29th of this month. I saw CAMH in January, and I'm still waiting (well, going ahead anyway) for their "results" to be sent to my family doctor.
I just LOVE the line in TransAmerica, where she asks the doctor if he doesn't find it strange that a "mental illness" requires drugs and surgery for treatment...