Vivek, although I would not recommend that you prepare a complete "end of life" plan, some advance prep may help you to remain calm. Advance medical directives and establishment of medical power of attorney may help you to ensure that your family understands your wishes and can communicate (legally) for you in the event that things go very badly. I prepared these documents, submitted them, then promptly stopped even thinking about them. They were there in case I no longer could manage my own affairs, but I had NO intent that they be called upon.
On the other hand, prior to my surgery, I did make sure that my wife had all of the account numbers at banks, brokers, or any other assets that she might not actually see in the home. I also made sure she had the relevant contact and policy information for my life insurance and medical insurance. Obviously she did not need to use this information, but she knew that should I become incapacitated, she had all the important financial information readily at hand.
I most definitely would not pay off all outstanding debts, loans, mortgages, etc., as I had every intent of continuing to meet my responsibilities. I did not tell bankers, insurance agents, or anyone else about my pending surgery - except for my employer and my immediate family. The others just do not need to know. You can choose who, among family and friends, you wish to tell, but you do not "owe" it to anyone other than immediate family and employer. Also, I would not sell stocks, bonds, mutual fund shares, etc., as this may cripple your accounts' ability to protect your assets' value and, depending upon the structure of your accounts, may trigger tax "events" that could needlessly cost you money at tax time.
Family generally understands all this. At work, I was pretty open about why I was going to be away for a while. I told my work friends and my staff what was coming up, as I wanted them to understand my viewpoint of how long I thought I would be off, and also I wanted them to know that when I first returned I would not be "at my best" but that was expected and I had no reason not to expect a full recovery. I did not want my staff to think that they would have to get used to a new boss at any time soon.
It is all rather personal. We all have different levels of comfort with sharing our situations. I shared facts, not so much feelings. To everyone aside from immediate family, I put on the strong, confident face that was just planning my return date. At home, I could share my fears, if I needed to. Most importantly, by the time I had my surgery, I knew full well that I could always come here and talk with others who had been down the same path I was facing. The advice and support here made it all a lot less scary.