[RESTAURATION] 1988 Stretch Limousine Lincoln Town Car

Hello everyone!
Little presentation to give you a better understanding.
A week ago, I just bought a car, actually my first car, for 777$, which happened to be a ridiculous 1988 Lincoln Town Car Stretch Limo. I never worked with cars, at all, but I'm strongly motivated, and I pretend I can learn from mistake and efficiently. Yes, I'm that unconscious young man who made a ridiculous deal haha!
https://imgur.com/odk3uYC

Thus after changing the battery, every essentials are working. From lights to the engine.


But I'm definitely going to change all the fluids, and all the filters.
Still, I don't know if I should replace the drive belts, spark plugs and radiator hoses as well.

I'm here, because I'm going to ask questions of various levels and topics around reparations.
And actually, the greatest problem I have right now, is mostly non-essential. I'm trying to figure out how to fix all the side electronics of that limousine. There are so many buttons which should control everything, from windows to lights, radio, sound system, driver/passenger window, etc...

I did eye check all the fuses and they look fine, but I might be wrong.
Thus I'm asking you for the moment.
What tools should I buy to figure out the electrical wiring problems, what should I look for and where?

Thank you very much for your understanding, and please bear with my current incompetence in the field.
https://imgur.com/CHAAigi
https://imgur.com/AfajHtX
https://imgur.com/kvcmTSS
https://imgur.com/RwA5NcU

https://imgur.com/RwA5NcU