I believe that there will be an guide for the Berlin event, but you would need to contact firstname.lastname@example.org to confirm. I have contacted them and will post their response once I receive it, but encourage you to contact them directly as well.
Regarding your questions about which exams to take, I would recommend starting off with the NetApp Certified Data Administrator (NS0-155 for 7-Mode or 157 for ONTAP) of the technology with which you are most comfortable. Our newer exams are all written towards ONTAP, so you should take that into consideration. While the NetApp Certified Suppot Engineer (NS0-191) recommends that you take the NS0-157 (NCDA ONTAP) it is not a requirement for the exam. Still, I would recommend both based on what you've shared. The two exams are independent and can be taken whenever you feel most comfortable.
Regarding the NetApp Certified Implementation Engineer exams, three of the four do require the NCDA. While you can take the test without having the NCDA, you will not earn the NCIE certification until the prerequisite NCDA is earned.
The Certification room (Hall 7, floor 3, room: Berlin 1) will be open the entire event and will be accepting walk-ins throughout the event as well. I recommend making your exam reservations now. Once you register for the event (through the www.netapp-insight.com login) you will be able to register for three exams. At the event, you can register for as many exams as our retake policy allows. During the event, I recommend that you stop by the Certification room earlier to make more reservations to ensure that you will be able to take as many exams as you would like.
Visit the individual exam Prepare tabs to start your preparation for the exams. These are the only NetApp approved resources to prepare for the exams prior to NetApp Insight.
If you have any more questions, please post them here, email me, or visit the Certification Help Desk in Berlin 1.
Best of luck and I will see you at Insight!
NetApp Certification and Accreditation Program Manager