I think its on the firewall under the hood
If that pickup used a 4L60E transmission (as would be typical for GM pickups with either a V6 or small block V8), yes.
The Flasher Relay for the 98 Lumina Sedan, (and all 97-03 GM W-Body
Open the hood there are to locking pin above each headlight assembly. Turn them you unlock them and pull the up. Once they are removed the headlight assembly can be removed.
The GM fuel pumps tend to be a bit pricy, plan to pay more than $100.
If it is a newer GM, you should be able to put the key in the "On" position for 10 minutes and the relay will reset itself.
Inside the alternator
Yeah, It is a right headlight assembly. Says "Guide" on the front of the headlight. From what I've research they seemed to have been a company that, in this case, supplied parts to GM as their OEM parts.
2003 model gm's do not have a cabin filter
Gm does not use inertia switches.
GM Ford Chrysler Toyota
GM calls the ElCamino a pickup in their literature.
GM does not have a 5.4 liter it's most likely the 5.3 liter.