Congratulations and welcome to the board. There are many resources including a large number of 500E owners here. Many questions or issues have been addressed and the search feature here works great in locating them. You should also go to "500e owner Roll Call" in the Hot Rod section and sign in.
I can add what others have already stated regarding the headrests. This has been checked by me dealer three times with no cure being made. They appear to be somewhat quirky and work when they want to.
94 E500 (Silver/Black)