Mixing old and new oil doesn't hurt anything. It just means you still need to do a full oil change when the oldest oil in the engine is due for it. The addition of new oil doesn't change when it's due.
I don't think you meant to say that you replaced the crankshaft. Probably the crankshaft position sensor.
What problem are you trying to fix? That single sentence you wrote is rambling and confusing. Clearer writing would make this easier. If you're old enough to drive you're old enough to write better than this. Sorry to sound insulting but when I see a question like this, I feel like it deserves it.
Overheating ruins older cars. Resolve not to ever let it get that hot again. Hopefully there wasn't serious damage done already.
You need to narrow down what's causing it to run hot. Make sure the fan works. Make sure the coolant level is correct, if you're losing any, figure out why. If it leaks, it probably only leaks under pressure when it's hot, so you might need to let it idle while you look. Coolant loss and fan are probably the 2 most common cooling issues in my opinion. But lots of things could be wrong.
If you don't know much about automotive cooling systems then do some research on that and learn more about how they work. Understanding the system allows you to intelligently diagnose cooling problems, and not just replace random parts out of desperation. It's a very important system to be able to maintain on an older car. Without a good cooling system your car will not live long, and it's a system that's prone to failures as a car ages.
If you're needing to add oil, then make sure you're checking it consistently. That's another thing that kills older cars.