Called about this issue a month ago.
The answer is, it depends on the week or system you have.
If your week is WorldMark, Starwood, Club intrawest, etc... these systems work a little different way. Developer will decide which week should be given to II, so individual owners have no control. Also, it is request first all the time, so until someone exchange something, II doesn't have actual week yet.
In this case, you cannot transfer deposited week to someone else, you need to reserve something and purchase a GC by paying $49.
If your week is from an independent resort (not a unique system like above), you can call a knowledgeable II rep and request transfer form and send them a fax.
I don't know if there's any fee, my week was a starwood week, so I couldn't use this option.