Freightliner/Cummins tech needed. Where is the lift pump and could it be my problem?

I have a 2006 Freightliner MT45 with a Cummins 5.9 in it. My problem first presented itself as a surging condition, during acceleration, that would go away if I shut the truck off and restarted it. Yesterday the surging got really bad, and now the truck will start and idle, then stall. I replaced the fuel filter and strainer... both were badly clogged with debris. The problem is still present. So far everyone I talk to says it could be the lift pump. Is the lift pump located in the tank? Is there a simple way to diagnose it? Does this sound like my problem?