Blue,
This is the most common rust area in an FE/FC, and unfortunately a rather difficult area to get at. Without knowing exactly where your rust problem is - there are a few different areas in there that might need work - I recommend you have a read of
this article here, about repairing/replacing sills on FE and FC models.
If you're lucky you might be able to cannibalise the other vehicles for replacement sections, but it's likely that if they've all been sitting together in the weather, they'll all have the same cancer-spots....
Anyway, hope you find the tech info page some help, and feel free to post questions here. As Jim mentioned, as a registered user you can post images with your messages, so if you have access to a digital camera, that would definitely assist in the remote diagnosis!
cheers
RET