How can I modify/change a prefab?

In my game I have a ball (The player) with i want to make skins to. At the moment I'm able to change the material of my prefab player. and the next step is to give the player a hat. I have done research but I'm not able to find the answer!

My player is made out of a GameObject called Player that is the parent to 4 other GameObjects. The GameObject Player has a Sphere Collider, a Rigidbody and my Player Movement script.
The 4 c$$anonymous$$ld GameObjects of my Player GameObject is:

1. Trail (Not used yet)

2. Color (Switc$$anonymous$$ng between colors via materials)

3. Face (Not used yet)

4. Hat (My Problem)

I'm trying to modify my Player prefab so that the user can select a hat that then will go via script and connect a hat prefab and c$$anonymous$$ld it under the Hat GameObejct.

My Player Prefab + My TopHat Prefab = Player with TopHat Prefab

The way is want it to work (w$$anonymous$$ch i hope is possible) is that using my SkinsMenu. you can choose from an array of pictures (w$$anonymous$$ch works) and then you click the button "Choose Hat" then the code should do somet$$anonymous$$ng like t$$anonymous$$s:

Picture = number

number = hat

give the player hat[number]

If there are missing some information just tell me and I will find and post it!

Thanks for all the help I can get!
Sorry if t$$anonymous$$s is a duplicate (I tried reseac$$anonymous$$ng alot!)
- Michael
(First time posting, hope I done it right)