First you can't just change the breaker.. The feed to the box has to be big enough to handle it.. And in this case I do not know. the box in my garage was 30 amps at 120/240 volt so it could handle it.. but.. I buried that line myself.
Second. MANY are the stories in these forums about people who had an electrician install a TT-30 for their RV and wound up with a disaster. The electrician wired it WRONG.
Better to have him install a 50 amp RV outlet. Those they get right. Now you can use 30 amp breakers (if the garage has the needed feed) but have him put in a 50 amp RV outlet and dogbone down to 30 for the rig if needed.
My 50 amp rv is mostly happy with 30 amps. In fact the generator is breakered at 30 amps times two legs.
