Hi. You might also try Spaceclaim as a Trial version and see if it can do what you need.:
http://www.spaceclaim.com/en/trial.aspx
Spaceclaim can directly open and save both Rhino and Sketchup files so maybe you can open the .3DM file with Spaceclaim and then save it out into Sketchup format.
I’m not sure what the restrictions of the trial version are though.