I recommand you to use MTA, its a usefull program if you would like to make your own mappings. A tutorial from how to use it is included when you start up the map editor in MTA.(If you don't find out how to start the map editor:
http://www.youtube.com/watch?v=URN4DWkR4cM)
http://www.multitheftauto.com/
Start up MTA, than click on the "Map Editor" tab, and build you own house, or whatever you want.
Second... searching the link from how to convert the mappings.
Here it is:
viewtopic.php?f=12&t=3332