2004 Suzuki Verona Getting Following Code P0174 P0171 P1512 Engine Light On

I am getting the following code from P0174, P0171 & P1512; the engine light is on. The mechanic wants to replace an oxygen censor. P1512 points to MTIA - mechanical failure. that thsi mechanic replaced last December($595). He claims it needs an adjustment, which he must do together with the replacemnt of the oxygen censor for $180. I hardly undrestand any of this. Is the mechanic correct? Thank you
Ben 347-643-4419