The best place to buy cheap Lego is from the Internet. Sites like eBay and Amazon are the best, and most reliable for purchasing Lego sets, minifigures, parts etc (new and old).
Try bricklink.com. It's pretty much a Lego marketplace where you can get used set and parts.
You can get replacement lego parts for specific sets. The best way to do this is often to go direct to the lego online shop, but it is also possible to get good quality replacement parts from and online auction site like ebay.
yes
One can buy cheap Razor Scooter parts from a number of online retailers. One can get them from 'Scooter Hut', 'Monster Scooter Parts' and 'Shop Razor'.
There is no Lego shop on Lego star wars 3, you have to buy the characters while they walk past you.
Cheap Lego sets can often be found on sites like eBay or Amazon.
you can sometimes get them from the Lego store on line but i am not sure if it is cheap about 300 dollars
Lego shop .com
you buy it at a Lego shop
ebay
The cheapest online shop for auto parts will depend on what make and model of car you have. If it is a general part then you can try jcwhitney or other online shops like them.