function replaceModel()
txd = engineLoadTXD("rcbandit.txd", 441 )
engineImportTXD(txd, 441)
dff = engineLoadDFF("rcbandit.dff", 441 )
engineReplaceModel(dff, 441)
end
addEventHandler ( "onClientResourceStart", getResourceRootElement(getThisResource()), replaceModel)
That's a clientside script, you put it in a serverside file.