Help starting with 3d printing

[jatgm1]

So I'm not a student in any official capacity, (other than not having he requisite knowledge) but I need help try to figure out how to design a chassis for a robot tank that would fit in an existing charger. I really want a remotely controlled robot with an articulable arm, movable camera using servos, and charging station/dock that can be driven onto to charge remotely.
I thought if i could make a chassis that fits the "robot buddy" aka "jinguang no. 777 325 i-tech tank"
If I can get the chassis to fit into the dock and replace all the existing hardware with something better, encoder motors, a raspberry pi unit, some h bridge units, and a place to mount custom stuff like an arm and cameras.
Honestly I just can't find a robot chassis that allows modifications and includes a charger dock. Lots of cool premade robots running ros2, none with a charging dock. The moorebot scout is terribly limited and not capable of what I need it for due to its small size

Can I somehow scan the machine with its wheels off to get a shape for the outside and somehow modify what the inside looks like? I'm not sure where to start trying to retro engineer this chassis .