Andy,
My situation is pretty similar to yours. I am 5 years older, a little taller, and about 20 pounds lighter than you and have been a competitive marathoner and rower for a good portion of my adult life. Also found via a precautionary CT scan for a calcium score. I'm at 5.0. Found out less than 6 months ago and am heading back for 6 month follow-up scan in a little over a month. It's been an adjustment in a number of ways and has taken me some time, so you should expect the mental sorting out process to take you some time as well (I've read studies that depression amongst people who were newly-diagnosed is not uncommon). For me, exercise has been a stress reliever and learning to dial back on the intensity of exercise while still exercising has been an adjustment. It's also been challenging because doctors tend not to give you objective guidelines for these things (I use a heart monitor to generally keep in a "zone 2" level of intensity and don't do any heavy lifting). My doc told me at 5.0 I am in a "gray" zone where most insurance will cover surgery, but I have some discretion about whether to wait until it hits 5.5 (which will likely be sometime in the next five years based on an average annual progression of 0.1) or elect to have it done now. Initially, I was leaning toward a wait and see approach, but more recently have been thinking about just having the procedure done later this year since I would be a decent candidate for successful surgery and for peace of mind. Good luck to you. The stories of others who have gone through this does help.