ian, welcome to the forum. Where in NY are you located...PM me if you like if you don't want to disclose publicly.
As for discontinued parts, all exhaust parts are "readily" available. Meaning you can purchase them but it may take some time to source them depending on where they are located.
First question is....how do you know you have an exhaust issue? Seems that you didn't realize this till the shop told you. An exhaust leak is noticeable. The common parts to rust are the pre catalytic converter pipes (there are very expensive parts appx $400 each - you have two).
I have a 92 that lived most it's life in the east coast and the entire exhaust from the main converter back has stayed in tact. This part of the exhaust is made from quality steel and is unlikely to rust away unless exposed to extreme winters (disclaimer - there are always exceptions).
I wouldn't rely solely on the dealer's claims. You may just need to have new gaskets installed. A little more investigating on your part may be necessary. When owning an SVX you will ultimately become more interested in cars and doing your own work...if nothing else than to save $3,300 for an exhaust. Owning a SVX while in high school can seriously limit your cash flow...hope you don't have a gf! j/k
