Cinder block buildings are notorious for being damp... exactly what you don't want in a reloading room or gunsmithing room.
Consider putting some furring strips on the walls and some foam hardboard insulation... and finishing the interior nicely. Keep down the temperature swings that will let humidity build up. In one segment of my garage, I don't have A/C, but I have a dehumidifier that drains out through the wall. That helps a lot! And I never have to empty it. But a nice room-size A/C would be a good investment.
Wiring is not hard. And you can do all the wiring first, then hook up your panel. Just leave the breakers to the end. You can get a small 8-breaker sub panel at Home Depot for a few bucks. Run all your circuits, test them with a 12V battery. Then at the end, hook up your panel and connect it. So you are doing everything 'dead.' When I did my reloading room, I wired it all before hooking up two power feeds. Easy as pie. The last two wires I shut off the main breaker to the building, wired them in by flashlight in about 10 minutes and all good. Only after I had tested the wires, BTW, did I put the pine walls up! You don't want to find a dead short... after you put up the walls!
But wiring is very simple. There are probably Youtube videos showing the steps.
One other tip.... draw yourself a wiring plan. Doesn't have to be fancy.... but decide how it's going to run. What is going to run what.
I bought LED Track lights, btw. Worked great! 6 little spotlights on a single track. Point them any direction. Then some strip lights on the benches.
There is a good thread in Reloading called "Building the Perfect Reloading Room." Lots of pictures and tips.
Hope this helps.
Cheers,
Sirhr