Maybe there is a LWO importer on
http://www.scriptspot.com .
BTW, LWO is not a "Doom3", but Lightwave format.
if you need to convert .lwo to .max you can use deepeploration from right hemisphere
http://www.righthemisphere.com/
it also converts loads of other formats, you can download a 30 day demo and use it for what you need