Paint sealant is like a manmade wax which forms a protective layer of polymers that protect the paint from UV rays from the sun, bird droppings, tar marks and it leaves a hydrophobic surface. The water beads and rolls right off your car so it is much easier to dry. It also makes your paint look clear and give crisp reflections.
You see paint fading, cracking, dulling over the years... if you give basic protection, it will remain glossy even after 10 years.
It needs a little base prep to be done right IMO. This is why i suggest you take it to a detailing center to do the major work. After that, you will only have to do the basic maintainance.
Even if you plan to go to a service station, buy this stuff and dont use anything other than this on your paint.-
Meguiars Wash and Wax
Washmitt
Supreme shine Microfibre towels
Meguiars spray wax or ultimate quick detailer.
These may cost a little bit but your car is worth far, far more.