A pillar corrosion

I have a '96 XE. I'm getting ready to sell the car - it is just not big enough for 2 kids' car seats - but I've just discovered that I have rust-through in the A-pillar, passenger side, close to the sill. There is also surface rust on the sill itself. The body guy at the dealership said Nissan has had this problem with the Sentras ("but don't quote me"). But he won't do the work under warranty because the warranty expired five weeks ago! So when I called Nissan Canada, they said it wasn't structural anyway, so the warranty actually expired more than a year ago.

Two questions for you Sentra fans: has anyone else had premature rusting (or can you send me to some sites where I can find out more)? And, how can I make the case that this is structural? I don't think Nissan Canada really wants me to buy a Toyota or Honda over five weeks worth of warranty coverage, although I would see their point over a year's worth.

Any advice would be appreciated.
Thanks.