As for work environment, I am forced to pretend I'm happy all the time. I have to smile and be so fake.I know that sucks. I work in an ice cream store, and it gets rough dealing with people all day. You always get someone who's rude to you, but you can't do anything about it, you still have to be courteous. But then there are the people who are more than friendly to you, and they make the job fun. That and the free ice cream with every shift.
If you aren't a "people person" (i.e. one of those that just likes everyone and has that crazy "happy switch") than a customer service position is simply not for you. While I know how you guys feel (I do wedding announcements for a newspaper, so have to be SUPER DUPER HAPPY to customers), I think that it would be more than a little rude to be bitchy to the bridezillas on the phone just because I am having a bad day. Of course, since it is on the phone, I don't have to smile or anything and can roll my eyes if someone goes off the deep end.
And as far as dressing goes, there is just one rule as far as I am concerned "Dress for the job that you want, not the job you have." That way you can be a "trendy artist" rather than a "trendy lawyer" (and both are trendy in their own ways). Although, to be fair, I knew a woman lawyer that dressed like a janitor and had a mustache.