Actually, there is a tool at most parts stores that's made to disconnect the old wires from the connector. If you have your new wires run down the column, then just remove a whatever color wire from the connector and replace it with the new wire in matching color.
It depends on the design of the crimped on terminal, specifically the method in which it locks in place. Some designs have a more than one tab that flip out to lock it in place. You'll probably need the aforementioned tool for that type. However on old cars like ours I only recall seeing a single tab. If you look close enough, with magnifying glass to aid the effort if needed, you can see what you have. In a single tab scenario, all you need is a small enough and long enough device to push in the gap and send that tab towards the center to unlock it, and then while depressed gently pull the wire out. I have a box of wood toothpicks in my shop that I use for this.
Here is a picture (that is only representative in nature, not an exact match for your application) that shows the flipped up tab. While inserting into the connector, the tab is compressed. When fully inserted, the tab springs back out and locks the terminal in place. What you need to do is compress the tab far enough to release it. It can be tricky, but I will grab the first wire that I'm going to work on, right up against the connector with my dominant hand. Then with my other hand I insert the toothpick and try to depress the tab. At this point I'll move my wrist so that I can put a slight pressure on the wire that I'm trying to pull out. With two fingers on the wire, right up at the connector, I'm using other parts of my hand to press against the connector to do this. Easy to do, but I'm finding it is not so easy to describe. So with a little pressure, and I do mean just a little, then I probe around with the toothpick. Once I get the tab depressed, the slight pulling pressure on the wire will result in a successful wire extraction. Hopefully this makes sense. Maybe I'll need to do a short video to show the technique.
Ok In this specific case there is plenty of room to use a number of solutions including the pen. I won’t say that the pen is mightier than other tools however. Using a toothpick I had the first connector out in 4 seconds