Radio replacement 91 M30

[Piffin]

Howdy gang,

I am the new owner of a 91 Infinity M30
Lucked into one that was a one owner with 52K original miles on it.
Leather seats have some stitching coming apart and I had to get the master cylinder and rear slaves replaced.

She goes like a bat out of hell now.

Previous owner said the sound system has not worked for a couple of years now.

Can I just replace with an aftermarket head/receiver or is this something so complicated that it takes diagnostics and all...?
I did get the AM to work for a couple of hours, then back to static all around again. Power antenna works when I turn power on.
I took it out to see if maybe there was loose wiring. Nothing obvious
I know nothing about sound systems other than have hear that this one is loopy and prone to early failure.