The relay for the fuel pump should be under the black cover marked electrical center. Switch out the relay next to it they should be the same. If no luck, most likely your fuel pump in the tank is bad as GM has had lots of fuel pump problems. My 2000 quit right after I entered a gas station.
Check your fuses!
check the fuel injectors
Could be the coolant temp sensor located next to the thermostat housing.
Check with a manual gauge (Thermometer) If still running hot Could be: Clogged radiator Bad radiator cap Water pump
The 1998 Chevy Express 1500 Van could have the 4.3, 5.0 or the 5.7 engine.
They could.
Could be a result from a bad spark plug(s), spark plug wire(s), distributor cap or rotor.
Take it to a mechanic. If you are asking that question on this forum then it is too complicated for you and you could mess up a lot of stuff if you do it wrong.
NO.
The EGR valve on a 1994 Chevy 1500 is located on the top of the engine. If the valve becomes stopped, the engine could idle rough or stall.
The 1998 Chevy Express 1500 Van could have the 4.3, 5.0 or the 5.7 engine.
Not enough vacume