Need a pic of a fuse panel

check this outhttps://www.elcaminostore.com/el-camino-emission-and-hose-routing-decal-305-c-i-5-0-automatic-transmission-california-code-xju-1984.html

www.gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/El-Camino/1983-Chevrolet-El-Camino.pdf

The position and function of the fuses is normally marked on the inside of the fuse box cover and also in the owner's handbook. If you are looking for a particular blown fuse, work your way through the fuses looking for a blown one. It is not difficult.

Yes there is and it should be under the dash driver side

I've never seen a fuse block that was bad enough to need replacement. generally speaking, one or a few connections may be bad or it may need to be taken apart and cleaned. At worst, you may need to re-route a few of the fuses. That can be done by splicing into the appropriate wires and running them to a smaller fuse block (you can usually get one at a marine supply house). The same but less neat approach is to just use an inline fuse for each and label them so you know what they serve. Most important is to use the proper gauge wire and the correct amp fuse (style does not matter..only amp rating)
Before buying it though, make sure you know what is working and what's not. Blaming a fuse box for a major problem with an important system could cause you major headaches later.
Look for wire splices and things that look non factory. People can mess things up worse than the car can do to itself.
As far as replacing one, you'd probably have a difficult time just finding one. then, cutting it out of the donor vehicle and re-wiring will likely not be terrible but is time consuming and you'd need to write down and diagram everything very accurately to get it back together without problems. Check before believing this but I'm pretty sure chevelle harness is the same as a 'camino.

Locate your aldl connector under dash near steering column. It should have 12 pin connector. Older cars had 8 pin connector. You can do either one. On 12 pin connector jump the last 2 pins, on top row, in connector with paperclip or wire. Turn on ignition till check engine light turns on. Count & write down how many times it flashes. It will flash for example 3 times stop then 1 time = 31 code. In older 8 pin connector jump the 2nd & 4th pins on top.

check or replace the bulb on the non working side

Lower right kick panel, at the bottom access hole.

Yes. GM made all Chevrolet El Camino's and GMC Caballero's excactly the same, save for badge and trim packages. You can interchange parts with El Camino/Malibu/Monte Carlo cars and some S-10 trim peices will fit. But all three Cars will interchange interior parts. as for the bumpers, Only El camino/Malibu/Caballero will fit without modifying them. A simple Bolt-On and go.

remove the vacuum line and either 2 nuts or 2 bolts holding it to intake manifold. clean gasket material from mating surfaces and reinstall.