my friend has a 02 duramax he changed the fuel filter & cannot get it runnining.... what do i need to do?

 

There is a primer on the bottom passenger side of the engine you should probably prime it.

 

I have not worked on a Duramax but my guess is that it can't be much different than any other diesel engine. None of them like air in their fuel. My guess is that either you have a air leak/seal problem. Check the seal rings.
I also recommend that your friend buy a service mannal for his truck.
Also their are allot of folks who wish they can service there trucks but some just can't, It may be a lack of tools or skills or ???? or who knows what. Sometimes it is better to take it to someone with the correct tools/skills.

I have been working on diesels for about 30 years now. I am not trying to be a smart @$$ but I am just calling them the way I see them.
See Ya
Chris