I have two plastic parts and they are actually designed to fit together in an assembly, but now they want to get it quoted as one part. So what i have been doing is bringing in one of the two parts into a new part, then bringing in the other part using>Insert>part and selecting my part. Finally where i am getting stuck is trying to COMBINE the two parts and merge as one...

I would have just simply re-modeled it to make everything cleaner, but it is a very intricate part with multiple contoure and other such features. I even tried to extrude between the two but keep getting the invalid geometry/zero thickness message..

Any suggestions??!