How do I fit a Raspberry Pi 3 into a DSLITE with controls

[LaoTzunem]

Hello!
Recently, my friend gave me his DS LITE so I just decided that I take the Raspberry Pi 3 B from my desk and actually make something cool with it. The big problem is, can I even fit the Pi in along with cables, and how the hell do I even plug in a controller psb?
The controller PSB from the DSLITE is fine but I don't know how to solder that onto the PI and make the controller work. Plus I'm not sure what I need to make the DSLITE.

Here is what I have and what I will probably need

I have a
Perfectly functional DSLITE (with pcbs battery screen everything)
Raspberry PI 3 B v1.2
32 gig sd card
useless working battery pack that i can open and reuse
70 dollars
30 dollar budget

i will probably need
a actual battery if the battery pack doesn't work
a raspberry pi zero
soldering tools
wires
solder
determination



can anyone list what else i need and how i could make this project and if you already know about a tutorial, can you send me it? I don't have a lot of tools so it would be helpful to list what tools i would need and yes i have tri wing screws