Should be relatively painless. You will want to make sure you have designated parameters that need to be synced up with same named parameters in Windchill.
If you have nested family tables, you my run into some issues. I don't recommend using nested family table within windchill.
I think the safest way to bring the objects in are to create a workspace, open from the original location and save. This will validate a lot of things. Have as much in session as possible to prevent ghost objects.
Parameters in formats may need to be updated if you want to have Windchill revision and version information. No easy way to do this other than making the new formats and replacing the format in each drawing. Fairly straight forward but a bit of a cumbersome task with hundreds of drawings.
Iguess other than that, not much more I can mention.