Mercedes 380SL 1981 Convertible

Have had this car since late 1990's. Two weeks ago, had seasonal oil change and check up. Runs reasonably well. Paint job is rusting in spots (see pictures) and I see some significant rust on the underside frame. It's a fun drive when the weather is good. Also, the back plastic window (part of the convertible roof) needs replacement or cleaning as it is increasingly clouded.