Extract the war3map.w3u, war3map.w3a, etc files with the MPQ Editor. Open world editor, and open the Object Editor. Use the
File -> Import Unit Settings (Same with Items and Abilities tab). Edit whatever you want via object editor.
After you edited everything, press the
File ->Export Unit Settings button. It will ask you to save a .w3u file. Save it as war3map.w3u. Do the same for items and abilities with their respective extensions.
Finally, add the war3map.w3* files back into the archive via MPQ Editor. Then your map should work.
If the mqp, however, has a folder named "units", first download this :
http://forum.wc3edit.net/useful-tools-f ... t1921.html Then extract everything in the Units folder into the SILK Objects Console -> Map folder. Run SILK Objects, and it should create the .w3* files for you.