Mods shouldn't be harmful to the game itself, they usually just have new looks and some gameplay changes, new weapons, vehicles etc. A few mods worth of downloading:
Turbo Jeeps:
http://www.bf1942files.com/file.info?ID=9223
It adds the ability to use turbo with the jeeps, press left mouse button to use the turbo thingy. <-That mod will give you a good laugh.
Merciless Historic Addon:
http://www.bf1942files.com/file.info?ID=9104
It replaces the loading screens, adds new crosshairs and various other little improvements such as historically accurate flags.