Hi everybody, I'm looking for any and all advice related to replacing a catalytic converter on a 2003 Galant ES model which is returning the P0421 code. I took it to a repair shop and they said the convertor needed to be replaced and that I was looking at around $900 with parts, labor and tax.

I'd like to do it myself instead and found a Pacesetter exhaust manifold with an integrated catalytic converter for $200 that should fit my model. Are there any resources available for installing one of these? I'm going to scour Youtube but just wanted to see if anybody here has any experience with these. I know bad O2 sensors can trigger this code too so I was going to see if I could check those as well.