Won't work for any pre 10/03 models .... except if you'd be willing to buy a new rear upper door. I have the soft close lock and looked into retrofitting it on my X5 without any luck as the lock does not even fit into the trunk lid....
The electric part is easy and not much work but the fitting issues with the new lock (it is larger than the original non-soft close lock) will make this mod somewhat unviable ....
- Jan