Hi Vivienne. I use an older version of Maya which all the new Collada plugins don't work with. My work around is to export out of Maya as an FBX then I use the Autodesk FBX Converter which is FREE. http://usa.autodesk.com/adsk/servlet/pc/item?siteID=123112&id=10775855#section7
There are versions there for Windows, Mac and Linux. If your program can not save in FBX format the converter can take OBJs and convert it to FBX then convert it a second time to Collada DAE using the same program. You will lose your normals and have to generate them in the upload window.
If you are able to export out of your own program as an FBX, as I do with my older Maya, you will not lose your normals when you use the Autodesk FBX Converter to make your Collada DAE files.
The Autodesk FBX Converter can also convert other formats to FBX as well. 3DS, DAE, DXF and of course OBJs. I have only tried it with OBJs. The FBX files and DAE files end up being bigger than when I export out of Maya as a FBX and then use the Autodesk FBX Converter but after I upload them to the open beta test grid and rez them they end up with the same prim costs and shape.
I haven't tried textures yet.
I hope this helps.