I just paid 1000 for a clean, rust-free, apparently solid grey market 500sel. All the electronic gizmos work. Is there anything anyone can warn me about? The only major issue is that the nitrogen spheres (part of the hydo pneumatic suspension) in the rear need to be replaced. Is this easy if anyone has done this? also it is possible to convert it to standard shocks. Has any one done this?

The car is incredible to drive (minus the bouncy rear) as I found out on the 90 mile drive home from where I bought it.