Yes the TDM can be confusing at times.

For the package file

The only thing you can do is make sure the place you are getting your package file from is on the same verions of I-Deas that you are on. ALso why Export out to step form I-Deas. It would so much easier modifying a part in I-Deas that has history than exporting out and working on a part without part history.

The only other way to get the information from your source is by using a universal file.

To do this hit CTRL+M to bring up the side menu Type in /xto in the comman line then go to file export then export app data.

This will export a universal file out with out library information. It just exports what is in your Model file.

What type of error do you get when you try to open the package file?