Get a poker, find the street valve and where the plumbing enters your house and poke between the two spots until you find it. Alternatively you could pull your plans from the city.
Don't use a ball valve unless you can trust your self to always do it slowly the shock to the system if you slam it closed can break old lines. The proper valve to install is a globe valve.
Just shut the water off at the street and put a shutoff on your main before it enters the house. Worth doing if you ever have a need for it should ideally be right before a hose bib so you can drain your line.
IMO we should have 4 years compensatory service after highschool either in the military or civilian services. Housing, food, medical, and pay provided during service (like the military). College paid for when finished, and or you come out with a trade certificate.