GPL license when using another's code

I've written a program I'm going to be distributing that uses a few subroutines from a free library (slatec). I assume I can distribute these files as well, but should I include the same copyright/licensing blurb in them as I do in my own actual source files?

I don't claim it as my own but state:

'This file is part of the slatec library and is used in foobar'

If you use GPL code in your app then you can NOT distribute your app without making the entire source code available under a compatible license (ie. the GPL).

Following that, you can redistribute GPL code at will. Leave the original license in tact, unless your the owner of the code you don't have the right to re-license.

*IANAL