https://connect.mayoclinic.org/discussion/what-i-learned-from-my-open-heart-surgery-part-1/
https://connect.mayoclinic.org/comment/1257983/
Hello @pinkpam,
"Blind sided" you typed...well, that's a perfect description of what myself and many others here on Connect who have had open heart surgery felt! So please do not feel alone in your fear.
Your profile says you've had a kidney transplant. May I ask if you felt the same fear facing that surgery?
The reason I ask is preparing for open heart surgery is not unlike preparing for any kind of big surgery.

I posted two links I made to share with others facing open heart surgery for any number of reasons. The route and routine is the same to get in and out of your chest, but the reasons differ and the post op course may differ.
But still there is a lot in common.

If you type in open heart surgery in the search area at the top of this screen it will lead you to numerous posts about open heart surgery. There is not a specific support group dedicated to just this surgery.

Are you able to get out and walk or exercise? Being healthy going into this is in your favor.
Do some reading on here on Connect and see if it doesn't help your fear level diminish just a bit.

When and where is your surgery being done?
Do you have supportive family or friends or neighbors to help afterwards?