In your situation, any worries about the car can be pushed back for at least a few months, so just make a calendar note to check on whether there’s anything wrong with it, then put it aside for now. With minimal driving it’s not getting worse, and may be nothing at all.
Follow all @backachu’s good advice, with this addition:
You have surgery tomorrow, so prioritize rest right now. Instead of thinking you have to hold onto everything, once you’ve written your list set aside several hours to let go of everything and rest. Something creeps back in your mind? Push it out. Repeat to yourself: “For my best outcome in surgery I need to be well rested. If possible I need to sleep. Resting is the most important thing I can be doing with my time right now.” If you can’t, don’t beat yourself up about it, treat yourself with the kindness you would show a friend. But if you can, it will help you react better to anesthesia and heal faster if you don’t go in depleted.