GMC Yukon, 2009 model Fuel tank issue and check engine light on

Hello,

I have a 2009 GMC Yukon, SLT (4WD). I have two issues;

1- While fueling the car with petrol, the fulling process stops frequently and the fuel station personal must hold the fuel pipe so the fulling process continues and he must do it in slow. If he speed up the fulling process the petrol will come out from the fuel tank and spells on the ground. I have checked with a friend and he said I have to change something called "canister assembly" and the issue will disappear.

2- I have check engine light on. It is not flickering but always on. I checked with a garage and they told the diagnoses shows these two errors:
P0420 : catalyst system low efficiency bank 1
P0430 : catalyst system low efficiency bank 2
and they advised me to change the catalyst and oxygen sensors (both bank 1 and bank 2).

Can you please advise me on how to solve these two issues.

Regards,

Aziz
e-mail: shamorig@omantel.net.om