A friend of a friend? Warning, warning, warning: Does he own/work in a shop that does this? How many of these tint jobs has he done? Your wife needs to take a look at some of this guy's previous work. Applying tint and doing well takes practice and skill, as well as a few special tools. (And good film is a lot more expensive than cheap film, but difference becomes readily apparent within a few years.
As far as laws go every state is different. I've seen the info on the web, but I don't remember where. I s'pose Google would be a place to start looking.