RAID 0 recovery
Things you might be able to recover from the remaining disk:
The file system header may be smaller than the stripe size of the RAID volume, so there is a chance it will reside on a single disk.
Files smaller than the RAID stripe size may also reside on a single disk, but you may not be able to recover sufficient file system metadata to infer the location. If the RAID set has more than two disks, there will be a greater chance of a small file spanning disks that are still functional.
The RAID header will reside on all of the disks, so if you can find documentation for the format you can at least identify the location of the actual volumes on the RAID set.
Depending on the filesystem used, there may be redundant storage of metadata at various points within the filesystem. IIRC, for example, the superblock of most EXT* filesystems is replicated in multiple locations.
It is likely to be possible to recover some small files where both the entire file and sufficient metadata to locate it reside on the same drive. On a deep directory tree this would also involve all intermediate directories, so the chances of recovering any given file are fairly small.
If you have some chance of identifying the file by content the directories might not matter. However, most likely scenarios where you could do that imply that you already had a copy of the file that you could compare it to.
First port of call would be to try a data recovery service on the dead disk.
Sorry, it is impossible. RAID 0 is striping across drives with no redundancy. You have no idea which bits of which files were written to specific drives.
Your data is still there, but in a probably-corrupted state.
Most of the time, the writes are interleaved between the drives. (but at what block size? who knows...)
It is theoretically possible to simply rebuild the header (or footer) of the drives if that is all that got corrupted. The header could alternatively be copied off of a new array and placed over the top of the old drives. However, there is a lot of proprietary voodoo involved.
To do a successful recovery you would definitely need to look at the spec on the RAID format, and inspect what went wrong with your RAID headers.