[John_F]

I suggest you look at the roleplay scripts here for examples.
There are tutorials on the tutorial board:
http://forum.sa-mp.com/forumdisplay.php?f=70

You can make buildings by "Mapping"

Cars can be added to your script by the line:
AddStaticVehicle(modelID, x-coordinate, y-coordinate, z-coordinate, color 1, color 2);

You can get the coordinates of a vehicle by going into any server, entering a vehicle, parking it the way you want it to spawn and doing /save

The locations will be saved in your gtasa folder where your samp is installed, it'll be in the file savedpositions

To get the cars in the script, add it to the pawn code.

You can get started with your server by downloading the server kit here:
http://www.sa-mp.com/download.php
the windows/linux server not the client. The client is used to play servers, but I'm sure you knew that already :P.