Any chance of a PPI? Test drive it after 5:30pm on Saturday then return early on Sunday to feel the upper radiator hose before the car has been started. There shouldn't be any pressure in the cooling system. Remove the reservoir cap and listen for a rush of air to confirm.

Most of the electrical problems could be fuses.

Is the side trim body color? It should be black for that model year. Check if it's been repainted and if so why.

There's an 87 300D buyer's guide floating around the archives.

Sixto
87 300D