I have questions on exhaust hope someone can help me with.

I have a 1.9 - my exhaust system is quitly rusting away - due for
replacement in next 6 months.
I'm thinking of replaceing it with a Stainless Steel system.

My questions:
1.
Anyone got a feel how much more a stainless system will cost over a
standard set-up.

2.
Would an extractor system get that much more performance benefits rather
than the standard set-up - or is the standard system efficient enuf that
you wouldn't notice?

3.
Being the environmental prick that I am - I'm thinking of putting a
catalyctic converter in the exhaust where there is none at present.
(Australian specs) Is it that symple - to just bolt in - so to speak. Will
it detract from either performance or economoy?

Thanks in advance.

David Del Ben
85 Vanagon