Q: I need to replace my catalytic converter and I wanted to see what are the main parts I will need to buy that comes with it?

The parts required to change out a catalytic convertor will really depend on what type of converter is going to be used. There are factory type replacements that will use a flange and just get bolted into place, that will require a new flange gasket and pipe clamp. Or there are aftermarket replacements that will require the pipe to be cut, and either welded, or clamped into place. Other than that, I would suggest that this is the perfect time to replace the oxygen sensor. Keep in mind, when removing the flange from the back of the engine, it is fairly common for the bolts and/or studs to break, due to all of the heat cycles that are associated with the exhaust/converter. As far as the rough starting issue, I would check the timing chain and tensioners. It sounds like there may be a possible issue with chain tensioner, and this can cause all kinds of problems, especially throwing off the timing and causing rough starting and running issues. If any of this sounds like something you could use a hand in diagnosing and/or repairing, contact a certified mechanic, like the mobile mechanics at YourMechanic.com.