I don't know about E60.
Use realoem.com to cross-check part numbers.
If you can change tire, you can do this except that you also need a jackstand to be safe.
They can charge one hour because: jacking up, tire removal, remove fender liner.
Take the reservoir to rinse it (not needed but since you are there, you may as well rinse it).
Not that hard if you want to do this.