I've had to replace the metal brake lines on both of my 1982 MB. Both were rusted on the inside as well as the outside. I think the fluid replacement in a good idea.
The other safety practice I encourage on older cars of any manufacture is that whenever I am taking one of the older cars out, as the engine is warming up, I literally STAND on the brake pedal. If something is going to fail, let it fail in the driveway, not on the road.