So a bit of good news arrived in the mail today. A letter from OK Speed Marketing stating that they have finally received my money from the wire transfer and included in the envelope was a voucher for the ride in the Ring-Taxi. So I went ahead and booked a ride with them on May 4th at 3:00 PM. So we'll have to leave early from Berlin to make it to Nurburg in time.
So good things come to people to wait and take chances! :)