Truck Repair: engine boggs as gas gets lower, dodge van, gas tank

Question
'05 Dodge van 3500 15 passinger. Engine boggs down stuttering and backfiring as gas tank get empty. It starts at 1/2/full and gets worse over time until I have to keep it full all the time. Yesterday it started to be very hard to start but ran fine on the Hwy. We had this problem once before and the mechanic changed a sensor or filter in the gas tank. It was rather expensive @ $200 plus.
I was wondering what the part is called and if this is something I can do myself with limited tools?

Answer
Hello Jack,
The filter should be in the line outside the tank, and if that is what he changed, he got to you bad.
If he changed the fuel pump, then that was a pretty good price, cause it is inside the tank, which usually needs to be removed to do it.

Tell me why you would be paying for repairs on an 05 van. It should still be under warranty.
Van