Adding maps to Clear Sky...

[Elite Mercenary]

Hello, I am a newbie at modding this game. I've extracted all of the files from the data bases, and I've been looking at other mods to see what was done. Anyway, I am trying to add maps from the previous stalker game to the game. The only issue is that I cannot access them, when I used the sv_changelevel command the level does not load. It gives me an error that such a level does not exist for single player. I have transferred the data entries to the maps_single.itx, game_levelsmusic.itx, and game_levels.itx (exact names?).
Anyway, any help or advice as to what I need to modify in order to get those levels to work would be appreciated!