Help with converters

[borderslegacy]

I have a 99 Legacy wagon, 30th Anniversary Edition with 2.2 engine.

The dealer was trying to track down a rattle from the exhaust and found the inside of both converters were loose and rattling. The problem is they say replacement will be about $1800 parts and labor.

The car was originally sold in California, so it has that emission package. I live in Minnesota, so I don't need to meet California emission tests (we have none here nor anticipate any). I did find after market (Calco and Eastern) units for about $400 total. Is there any problems using these converters?

And what should I anticipate when my husband goes to replace them?

The car has about 165K on it and, except for probably being due for a timing belt, otherwise runs great.