DSS is the name of a company that sells motors and other various parts
A shortblock will consist of just the block, with the crankshaft/rods/pistons all assembled
A longblock has the same as a shortblock as well as the heads installed. Some you can buy with a cam and timing chain installed too but not many.
you dont sound ignorant, you gotta start somewhere
no matter what you buy, you do NOT want to use the stock intake. With the money you spend from the $3000 motor you were thinking about, you can easily buy a very nice intake, cam, and set of heads