What do you mean by 'import this class library'? Do you mean just adding the
Imports statement on top of the source file (or in the project properties)?
The Imports statement does not 'import' anything as such. If you have a
class library, you simply add its reference to your application and then use
the Imports statement simply to be able to reference members from the class
library without explicit qualifications. That's all the Imports statement
does. Your class library exists as a seperate assembly - either in the GAC
if its a global one or in your application folder (being copied over). So as
such, what ever code you write in your application is what makes up your
assembly size. Ofcourse, since the application is dependent on the class
library, you need to deploy the class library as well - regardless whether
you are using only class or many classes from the library - along with your
application whenever you do so. That should pretty much answer all three of
your questions.

hope that helps..
Imran.