This is a way to talk about something that you're imagining might happen:

Gosh, how great would it be if you got that job?

This means something like "If you got that job, it would be great, wouldn't it?" You would answer like this:

Yeah, that would be awesome!

Here's another similar expression, using "much" instead of an adjective like "great":

Look at that! Man, how much would it hurt if you got bitten by that thing!