Please help me answer questions about the Zumo before I buy

I will be buying the Arduino Zumo kit, motors and everything.

I DO want to use the infrared sensor so I can do mazes/follow lines if I want, but I also want to be able to convert it to a robot that uses a ping sensor to avoid hitting a wall (i.e. turn before), follow a flashlight beam, follow the source of a sound, detect dust and drive towards it, etc.

But for the love of everything, I can’t seem to figure out how to access the pins should I want to.

This would be an example image of what I intend to add so I can add modules ON TOP of the robot:

From what I understand, I can add headers to the expansion bay part in front of the Zumo shield, but 24 of the pins are used by the sensor (I understand 12 are actually used, and the others aren’t), but there are 24 pins. The Sensor also ends up blocking the headers should I only solder the ones I want.

I probably am missing obvious things, but can anyone help me out please?

Hello.

The Zumo shield does have free pins that you can use for connecting other sensors (even with the Zumo reflectance array attached). There are a lot of different combinations of features that could result in different pins being available. You might find this post by Jon helpful. As his post mentions, the “Arduino pin assignment table” section of the Zumo user’s guide is a good way of seeing what the different pins are used for. Additional information about the pins used by the Zumo reflectance array can be found in the “Adding a Zumo reflectance sensor array (optional)” section of the user’s guide. By comparing this information with the “Front expansion” section, you should be able to determine where the connections can be made.

Also, it looks like the picture you referenced came from Pentura Labs’s Blog. Their "It Can See; Giving Your Bot Sight!"post details which parts and pins they used in their project.

-Brandon