OK, so it's an uber masculine work place. What is that exactly? Do any women work there? I presume so and presume they are not uber masculine. Coming out at work is an issue that many trans people face about their transition. I've seen quite a few say the same as you and then they went on to transition successfully at work. Many are still on the forum and I hope they reply.
You say you don't want to throw away years of hard work but one would hope that if you are an asset to the company then they will still want your skill, experience and expertise. If not, there is most likely somewhere else that does.
Transition usually means you realign with the women who work there and even in an masculine workplace that would be no exception. Yes, you may very well lose a lot of male bonding time and chest thumping/bumping that goes on in those places, but that has more to do with the male/female dynamic than anything else.
Also, you might find, once you are on HRT for a while, you have less interested in an uber masculine workplace anyway.
I'd suggest that instead of getting anxious you look into the policy the company has (if any) around trans people and transition and start working towards the likelihood of transition at work. Ask questions on the forum for more feedback.
