It looks like a few white coolant spots around the neck of the radiator. Has there been recent work? The E39 540 is notorious for cooling problems, although if preventive maintenance is performed, it's not a problem. I would be checking to see if there has been work done and if it was done on a preventive basis or a repair. If it was a repair, what was the failure and did the engine suffer damage because of an overheat situation.

Check the operation of the inside fan control. Speeds 1-4 should operate smoothly, listen for the fan speed to increase or decrease while on one position setting. There is a $50 final stage resistor that controls the fan speed.

The air bag cover will always be out of line. The design isn't the greatest. You can unsnap it and straighten it out but the sun will work on it again.

You might do a search on the Roadfly E39 forum for any concerns, they have a tight knit group that are very knowledgeable about the E39, most of them own 540's...

Good luck with your decision.
JR