Event,
That would be No and No. Since you are not the producer (i.e. the initiating entity) of the project and are doing the work as a Work for Hire, you are not responsible for the content. Now that said, make sure that you have some written documentation in the WHA about you not being responsible for copyrighted material present in the project content. More so for the shooting than the editing but it wouldn't kill you to be covered by both.
Where the real 'responsibility' comes in is how the copyrighted material within the final product is distributed. If it's being sold in any form without the expressed permission of the copyright holder or his/her legal representatives, that's a no-no. Yeah, there are degrees of what might be gotten away with before someone takes notice and then action. But these days it's just not worth the potential hassle.
Even non-profit distribution efforts like on the 'Tube or other social networking sites are drawing serious fire from the entities that own copyrighted content. So to keep your 'end' out of the line of fire, make sure you inform your client of your stance on this issue. If they wish to go ahead, then make sure you have your disclaimer in the written record. The odds of something going down used to be small, but they're getting bigger every day so CYA!
