When I push the pilot knob, I can light the pilot, but after keeping the knob down for a minute, when I let go, the pilot doesn't stay on.

You need a new thermocouple. They all go bad after a few years. You can buy a universal replacement at almost any hardware store. When you put in the new one make sure to adjust it so just the 1/2 inch on the tip is in the flame. You can recognize it because it is the copper rod that is next to the pilot light with a copper capillary tube that is screwed into the gas valve. Turn off gas and remove the part screwed onto burner that holds the pilot light tube and the thermocouple. Unhook both from gas valve. You can then replace it easily and take this assembly to hardware store to match it as there are different types. After replacing it you will have to light the pilot light and adjust it, but if you have the new one with the same length from the assembly as the old one it should be correct most of the time, if not make sure to adjust it so only 1/2" of the tip is in the pilot light flame. DrTom4444