Not sure if it's possible, but I'm pretty sure if you have Nav on your car BMW will load EU maps onto it for you to use during ED, and then your dealer can update to NA maps once it's back.
If you weren't planning on Nav, I'd recommend it strongly, along with the whole tech package. LOVE the HUD. If you do have it, then just use that to find nearby gas stations.
I'm sure you can arrange flexible car drop off location and times if you wanted to do most of the trip by train. Me personally, I'm gonna drive the heck outa my car once I do a ED.