Is there any benefit in having a 40 amp AC charger if my shore power is 30 amps? Should I change to a 30 amp charger?
Actually we need to differentiate between AC and DC voltage and amps.
Your 40 Amp 12 VDC charger (aka converter) is powered via 120 Volts and runs at less than 5 amps AC. The output of the charger is 40 amps at 12VDC. Therefore you can keep your 30 amp 40 120V receptacle and run your 40 amp charger no problem.