How can I get the stairs to come over to the plane so the passengers can board?
You mean the stairs on a truck, that would have to be a pay add-on.
See if this appeals to you, (don't drink the water).
http://www.lagosim.com/ They are having server problems now so I can't access their products but I think you'll find what you are looking for here.
If you turn the default scenery all the way to extremely dense, you will get trucks, cranes and the jetways coming from the gates.
I have just turned my default scenery all the way up, as never tried it before, (presumed my system couldn't cope!), but i cant see any trucks etc, where have you seen them or am i doing something wrong??