Welcome to the forum.
I don't have any recommendations for T.O. but I can offer some info.
There is a U.S company, Battee.com whose specialty is the C4 instrument cluster.
The delcobose radio is a complicated beast, amps in each speaker, separate head and amp for the unit. There is a lot of info on the net for troubleshooting this so maybe you can narrow down the problem. If not you'll need to get your wallet out. Going to aftermarket can be done but takes some expertise to deal with the complex bose components. There are a number of U.S. suppliers that offer rebuilding services
The climate control buttons are, apparently, easy to clean, again a google search will turn up something.
There is info in this forum and good videos through Corvette Central.
Good Luck