audio upgrades are 99% plug and play. Even if the grips need changing you fitter can cut open the wire without cutting original grips.
Woofer, Amplifier would need wiring from the battery, That also doesnt include and wire cutting but extra load on the electrics of the car.
The only problem is speaker upgrades would / might need fitting changes in the door, they often hammer holes for new speakers and aqalmand admi would put wooden spacers on orignal holes and and install new speakers on them.
I am not sure if the unit audio is bad or speakers.