Solid imported from solidworks

I have a complex shape that I imported from a graphical designer. I now need to turn the shape into a two part plastic piece that can be molded. I need to start with making the part a shell however because of all the small detail on the part such as embosses and the like, the shell feature won't work. I can split the part with little issue if I use planes however I need to remove some of the finer detail and then add it back after the shell is created. Is there any way to turn curved surfaces into the split tool plane to split these details off? I mostly work with sheet

Can you zip and attach the file here?

Without the file only general advice can be given.

Have you gone through the tutorials in my signature?

I have but I'm not sure that I have found what i am looking for. Perhaps you could suggest one. I would rather not post the file for all to see is there somewhere I could send it to you directly. Also, I think the file may be too large to email in SLDPRT file. I also have an X_T file type that may be a bit smaller.