Our first recommendation is that you get a second opinion. Have this Toyota Camry looked at by another smog check repair station, preferable a STAR certified smog check and repair facility. You may very well need all the repairs the first shop has mentioned however it is not very common to require repairs in all emissions component systems AND require replacements of CAT. Furthermore these catalytic converter do not need to be purchased at the dealer. California approved aftermarket CATs do exist for 2000 Toyota Camry at a significantly lower price than the dealership item.
P0430 is indicating that your Nissan Maxima's CAT may not be working properly. P0430 could be falsely trigger due to a leak in the exhaust manifold or intake manifold. We recommend replacing your Nissan Maxima catalytic converter only after inspecting the rear oxygen sensor to ensure the oxygen sensor is not sending a lazy signal to the ECU (engine control unit). You should ensure the oxygen sensor is working and also ensure the oxygen sensor is communicating properly with the ECU prior to replacing the CATs.
