You don't want the 3.8.3 Web Services version. You want the 2.8.3 (Current) version.
The standard workflow, in a broadcast environment, is as follows: A newsroom system (NCS) receives news feeds from news agencies i.e. Reuters; The textual content is edited in the NCS; At the same time (and all the time) the NCS is receiving <mosObj> messages which come from media management systems (Mos Object Servers) (this contains the objIDs that you asked about); Relevant objects are added to the textual content in a playlist system (usually part of the NCS) which builds running orders of news stories; When the running order is complete it is published by the NCS and split up and sent to the relevant mos servers in an <roCreate> tag (you need to read the protocol for finer detail) (in a TV production this would probably include teleprompters).
In your situation I don't know where your media objects are coming from (or even if you use any). If you only want to post the textual content of the stories that people enter on your site to WinPlus, then you are having the same issue that we have, namely, which tag in a Profile 2 mos message do you use to hold the texual content. You may need to approach WinPlus and ask them for the specific answer to that question, in fact, try to get them to send you an example mos message that their system typically sends them (if you manage to get an example then I'd be rather interested in seeing it myself).
Sorry that I haven't been able to exactly answer your question, but hopefully I've managed to help your understanding of Mos.
Regards
Mike