Long story, short...pull the Bose and the amps, wire in a good Sony or Pioneer head unit (Bluetooth!) with new wiring to the speakers. Don't attempt to splice into or use the old speaker wire. Crutchfield has good prices on stereos/speakers, and will sell you wiring adapters at a reduced price. If installation is beyond your means, ask around for a good stereo shop...as in don't go to Best Buy. Spend your money wisely he first time.
The ribbon cable in your antenna is probably shot, why the antenna won't extend fully. You can buy replacement parts for that, or again ask a stereo shop.
Not exactly your vehicle (this is my '96), but this is what's possible. Plan wisely. BTW, doesn't everyone have a pic of their car on their stereo?
Stereo Pic
(life-sized image modified to link-aapple)
|UPDATED|9/1/2017 7:26:39 PM (AZT)|/UPDATED|
______________
1973 Mille Miglia Red LS5 - SOLD
1981 Dark Claret Metallic - SOLD
1982 White
94 Torch Red LT1
96 Dark Purple Metallic LT4
02 Black Convertible - SOLD
03 Millennium Yellow Z06
09 Atomic Orange Z51