Here's a link on how to configure grids for the viewer, http://opensimulator.org/wiki/Viewer
If they're running a mesh enabled simulator and running a stand alone simulator, instead of using hosted service like Second Life or Inworlds, they need to configure the sim, http://metatek.blogspot.com/2011/07/multi-user-sim-on-stick.html also check http://opensimulator.org
If you have a mesh enabled browser, when you click build, select upload and don't see model, either the sim or the region isn't mesh enabled. If it's standalone they need to back up their inventory, OAR files then install a newer version, OpenSim 0.7.2 is mesh enabled. If you're using a hosted service, you're SOL.
As a precaution, export the model as both obj and collada, and use MeshLab to import the obj to export as a collada. There's still a problem with uploading SketchUp exported collada files, it's either the exporter or artifacts in the model.