It's certainly possible -- but before you do that, you might want to try some of the other sources for models listed here. The Trimble Sketchup 3d Warehouse is a particularly rich resource with a number of brand-name items often contributed by the vendor. (To use 3D Warehouse models in SweetHome3D, click the 'Download" button in the upper right of the model page and select either 'Google Earth KMZ' or 'Collada' as the model type. Save the model to disk, and then import it into SH3D.)
If you still need custom models after this, feel free to PM me here.
Maz
