good exhaust components diagnostic place?

[Dumbass17]

my truck has a misfiring cylinder and it can be a few things as found on the net anyways, these include
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)

where is a decent price i can get my catalytic converter inspected/replaced?

i'm going outside to check the plugs and coil now, i plan on replacing the plugs/wires and oxygen sensors myself but want someone to inspect/replace my cats

thanks in advnace