In the line that hooks to the passenger side of the intake manifold.
There isn't one.
The heater box is all electric on a 2004 Dodge Ram.
It is on the top of the transfer case.
A 1998 Dodge Ram does not have EGR.
yes
There wasn't a 1998 Dodge Ram 1500 diesel.
A 1998 Ram did not have EGR.
no
Yes it should.
No.
A 1996 Dodge Ram pickup truck vacuum hose listing and diagram can be obtained from most Dodge dealerships. Many auto-parts stores will have the diagram.