I hope this is not out of line to share our link.. but seems appropriate in this situation..
We have a site dedicated to the modding of the BF1942 MP Demo.. for the most part many of the mods and general rules do apply, but you'll find it is a bit more restricted.
The main issue when people attempt to modify the demo they try to repack the modified RFA containers. This leads them to the Debug Errors.
In the demo you must not repack the RFA container and you can not directly alter the Objects.RFA or many of the other files.
Essentially all you need to do is extract the Demo_Wake.rfa and Demo_Wake_001.rfa files to the root and leave them extracted.. makes modding much quicker i find.
You'll find tutorials and various mods that have been successful on the BF1942 MP Demo on our site.
http://www.bf1942demo.com