The AS4700.2 standard is the one on which our HL7 is based it's freely available from the Standards Australia publisher SAI Global. The HL7.org documentation is useful, however you must be a member of HL7 Australia to access the standards, which is very inexpensive and it the best way to get hold of the standards. HL7 Australia
The following link will provide you the AS4700.x series of standards. Find the latest AS4700.2 and HB262 documents.
HL72.3.1 International spec is available on the HL7 Australia website as a free download: http://www.hl7.com.au/V2-Resources.htm
The simplest way we generally set up message exchange is via message files on the file system. 1 message per file. Drop them in a directory. We can also provide you with acknowledgements so that you can determine in your software how far the message has gone through the network. eg. is it waiting to route, on the hard disk at the other end waiting for an application to process, or it has been imported into the system successfully.
Once you have prepared your message, please use the AHML testing system to verify your message against the relevant profiles. Visit http://ahml.scem.westernsydney.edu.au/. The use of this site is free, you just need to register an account. Also download and use our HL7 Lint testing tool on your example messages. HL7 Lint will check for common mistakes and ensure items necessary for transmission on the Medical-Objects network are populated properly.