New Guy, 72 Plymouth Duster, where to start looking?

:welcome: from :canada:

Nice to keep your dad's car in the family but it sounds like you are going to have to do some work to make it a daily driver.
Get a mechanical oil pressure gauge and see what the actual oil pressure is. Very possibly the sending unit is bad, same with the temperature, you can use a basic oven thermometer to get a reading from the coolant with the cap off, just don't try to remove when the engine is hot as you may get scalded with hot coolant.
There are various forums for different subject here, and lots of extremely knowledgeable people who are always willing to help you. Provide as much information as you can about the car, engine, and specific issues or problems with each question so that you can get the best answers. Good luck!