Replacing my cat
 

Hey everyone, had a question for you guys. I'm running a 2003 VW Jetta 1.8T and am looking to replace my catalytic converter (no, not the fuzzball my girl calls a pet). I've been doing some research, but came into some hard questions that I can't quite solve.

First off, I'm looking at aftermarket. Reason being that $1,200 is just too much for the OEM part. The problem is that my mechanic swears on his life an aftermarket converter will die within a year; I imagine he'd like me to swing three times the price of aftermarket, but if he's serious, I'm worried I'll have to deal with this again next year. What do you guys think? Is there any reason not to go with aftermarket?

If there's no problems with it that anyone can really think of, I'm debating whether I should go with Walker or Magnaflow, such as part #54473 or #448773 on Autozone. I'm getting the direct fit since I don't know how to weld and don't have any folks in state that could help me with it.

Some other concerns I'm coming to; I have oil going in to my intercooler from the turbo. Not a lot, but enough that a previous mechanic brought it up. Would this be a potential candidate for reason why my cat might die? I'm very unfamiliar with turbo engines, so I'm a little lost on the subject, and Googling really hasn't yielded much in the way of conclusive information.

I'm working on a budget here, so I haven't stopped by a specialty shop, and the dealer has already ripped me off pretty hard on other issues so I'm pretty hesitant about going near them if I don't have to...