I suppose that would be pretty campaign dependent, but in general, the common populace would not have a huge reaction to someone becoming a slobbish dragonborn, save for the initial shock of a previously not scaly person suddenly becoming one. Unlike the dragonborns of Bahamut, who swear oaths to fight against evil dragons, the slobbish dragonborn are only “bound” by their desire for easily attained power, but since it’s power that can be used for good or evil, it’s really up to the character and their actions how people will react to them (I sought power to defeat evil vs. I sought power to indulge myself).
For the person becoming a slobbish dragonborn, again, its up to the person. Someone who enjoys eating a bunch is gonna be thrilled by a mission to keep themselves stuffed for a whole day, while a more reserved person might see it as a chore to get over with. Once the stuffing is done, they’ll be asleep in the egg, and wont feel themselves change until they step out of it, but their senses will have been changed slightly. The wisdom damage and fat soul might turn them into more of a slob, if they were not one already, or make a persons unhealthy tendencies even worse. With the right power selection, they may even drag the people around them into slobhood, intentionally or not.
Since slobbish dragons are generally neutral, and pretty dumb, getting them to agree to give a person some scales to use for the ritual shouldn’t be too hard, if you’re clever enough and good at talking.