Actually its pretty simple and you don't have to modify conversations.apk. You should do the following things:
1. Navigate with e.g. root explorer to /system/etc/customization/settings/com/sonyericsson/conversations/
2. Open custom_settings.xml w...
It is possible to remove this warning message as long as you are rooted. You just have to delete (or move to different directory) LearningClient.apk from /system/app. I haven't found any side effects of this.
There is easy way to get rid of the splash logo. Just replace the kernel/repack-ramdisk.sh (simple drag&drop in winrar/winzip) in the HellsDoctor2_R18.zip with the following file:
You can change these values with e.g. this application https://market.android.com/details?id=com.lim.android.automemman&feature=search_result
zephiK, in Chroma 5.1 there used to be a "national roaming" setting. Would you be able to bring back this feature to Chroma 6.0? It's really useful to me (and many EU users).