Mission Critical system

Hi,

I received my F-250 NetApp storage device, I am very new to this system, and I never used them before. I have the following questions and your help is much appreciated:

1- I will host many applications file to the netapp (oracle database files, control files, windows users files, linux files), the guy who installed the netapp for us used one aggregate with RAID4, one spare disk and one parity. Is this setup good for my case?
2- Which is better for Oracle, NFS mount or Iscsi? I am running RedHat 4E.
3- What is the best practice to use snapshots? Any documenation? What is the best size?
4- Does the snapshot make an exact copy of the volume or only delta version? Is 20% enough?
5- How I can configure multipath for linux? Which means I have my oracle database files hosted in netapp volume, I need to be able to reach these files from different paths, in case on path went down I can go to other path (system will automatically)? how I can do that?

6- Can I share a lun with multiple Windows servers using ISCSI?

7- Why should I get Snap Manger for Oracle since I have snapshot?

Thanks
Rami