Amazon always used to display their account number hyphenated, hence that is the format that is/was supported.
For scripts you want in both the S3 and EBS sections you could do something as follows:
- "stuff that runs for all (e.g. for both s3 and ebs in this case, and raw image too)"
- s3 only thing
- ebs only thing
AFAIK Xen stuff should work out of the box for cetain releases, but if not, try installing some of the xen kernels manually.