Also, if you are near the Twin Cities, or any other largish towns, you probably have access to an informed concent doctor or seven. I am all for therapy, I just do not like putting my choices and personal strength in the hands of a therapist. You should be able to get your blood tested and start HRT without a therapist's permission. That will make things easier all around, as it will show your therapist you are the type of football loving, gloc packing, amateur astronomer that can do things without having her hand held at every step of the way.
Your question in the title line made me smile. If it were true, and we'd have to drop all masculine habits and hobbies in order to properly transition, most of us still would, but it is beyond OK to just be yourself, do what you enjoy. As others have said, some hobbies may change over time, I actually think this is due to time management, getting done up and made up, having your hair did, shoe shopping... etc. and you may find these new time killers become new hobbies, and you just don't have as much time for Starcraft, you know?