Remember, there are two types of chinese - Simplified and Traditional Chinese.
The language packs are available for any version directly from JDE (Oracle) - just put in a Service Request, and they'll make the correct language pack available to you. I just did this for an Xe customer just a couple of months ago, and it took Oracle just 4-5 hours to get me the language pack.
Simplified Chinese has always been a Tier 1 language, Traditional Chinese has been a Tier 1 I think since 8.9 or so.
There is a HUGE impact on implementing Chinese on an existing implementation if you're on a non-unicode version of JDE. If you're on a unicode version (above 8.9) then it is installed just like any other language.
If you're running Xe/8.0 - then you cannot support unicode, so its important to understand that your installation can only support 1 doublebyte language (I can provide a lot of reasons why/how this occurs). If you're already using Japanese or Korean, for example, then either you install as a completely separate instance - or you need to upgrade to support more than two doublebyte languages.
I recently put a thread up on my experiences with implementing Simplified Chinese on here. Look at my posts in the last couple of months using the search function.
