Coolant Leak and Cracked Overflow

[Legokcen]

Good evening. Unfortunately, I have another question for you all. I'm learning a lot about this car though!

2008, 3.0, 55K (yes, very low miles). Everything has been great and today I had an issue. I went over to a friend's shop to pick up something fabricated. While there, the car was idling and we were having a conversation for about 3-5 minutes. I turned around to turn the car off thinking we were going to talk more and when I did, I saw steam rising from around the hood. When I walked to the front of the car, I saw coolant pouring out and puddling under the driver's side. When I popped the hood, I saw that the overflow tank was cracked down the side and spewing coolant.

I've done some research and realize that this has happened to others. I've ordered the needed parts to replace the tank and cap, but am concerned that there may be other issues. I was surprised that the tank was under pressure; I'm used an overflow tank not being pressurized. I am just surprised this happened while the car was idling.

I've included two pictures. When the cap was removed and more water was put in the tank (all we had) once the engine was started, it started to gush out the top. I know now it's supposed to be under pressure.

Is there anything else I should look into? Or is this an example of old, aging plastic, and it happens to a 12 year old car? I hope it's just the overflow, but if there is more I need to do, please let me know. Pictures are attached. Thanks in advance for the help.

First picture, the overflow with the crack in the front. Coolant was spraying and coming out.

Second picture, what we saw with the engine running with the lid off.