Diagnostic Code Puzzle!

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Hi all!

A mechanic told me (for free) that my 00 Mirage has these 2 codes:

P0100 OBD-II Trouble Code
Mass Air Flow (MAF) Circuit Malfunction

A code P0100 may mean that one or more of the following has happened:

The MAF may be disconnected, or a wiring connection may be bad
The MAF sensor may be faulty

P0421 OBD-II Trouble Code
Warm Up Catalyst Efficiency Below Threshold (Bank 1)

A code P0421 may mean that one or more of the following has happened:

The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
A sparkplug is fouled up

Do these 2 codes in combination mean the catalytic convertor will probably need replacement?

Thanks for any insight