If you are only going to be here for a couple of weeks, I wouldn't bother with the toll road transponder. It's useful for people commuting daily but I don't think you will be driving in rush hour in the same direction everyday.
Valet parking etiquette is simple... You hand over the key and get a claim ticket. Some place you have to pay first, then wait for your car. Some place you pay the guy that fetches your car. It depends. As for tip, generally, you tip just before you get in the car. I tip based on how far these guys have to go to fetch my car. If it is just 10 meters away in the same parking lot where I could have just drove off myself, they get nothing. If they have to cross a busy street, climb a hill, dodge a street fight, and get in some dark ally 3 blocks away behind a plus size women's gym, they get $5. If the effort is some where in between, $2 or $3.