88 Buick Riviera with touchscreen. remote radio :(

In My 1988 Buick Riviera there is a CRT touchscreen…its cool. it controls everything from the Radio to the Climate control…it even has a built in code reader and ECM diagnostics tool! (freaking amazing)…this all came stock when the car was brand new….. i want to be able to add an auxiliary input and farther down the road add a sub and an amp..i have an aux input through the tape deck and a radio transmitter from wally worl but lets be honest, they suck… The radio head itself is separate and in the center console, hidden. the CRT displays everything it does…. I dont know if the touchscreen just displays what the radio is doing ( in which case i may just be able to buy a new radio, and hopfully the screen will control it) or if its hard wired and an after market stereo is out the question. unless i bypass the entire OEM stereo that is. does anybody have any experience with this particular setup? they’re kinda rare so info is super hard to find…