Take the batteries back and then slow right down in the planning. A good electrical system suited to your needs takes time to plan out.
If you're never going to be away from shore power then a lot of stuff isn't going to be needed at all.
If you ever want to power a fridge and other 12V (or 120V) when not hooked up to shore power then a whole different ball game comes in to play.
If you want to be able to stay over at a job site and have a fridge, lights and perhaps tv then you may want to permanently wire the van to accommodate those needs.
If it's all 120V then you need one system and a way of hooking up the van to it. If some of it is 12V then you need a converter to take 120V down to 12V. If you install a battery bank and also want to use 120V then you need an inverter to take 12V up to 120V.
My van, for example, is wired for alternator charging of a battery bank when I'm driving, portable solar charging and shore power/generator charging. But I have a full and fairly complex system because I boondock almost 100% of the time and need a fair amount of power. I can run either or both 120 and 12V on an integrated system but that entails inverter, solar panels, solar charge controller, fuse block, 4 - 6V batteries, a battery charger, two inlets (1 solar, 1 120V), a solenoid, numerous fuses and an electrical sub panel with circuit breakers and a whole lot of wiring....
. Oh and power cords and generator.
Personally, I prefer separate components over inverter/chargers or converter/chargers. Getting one thing to do two things superbly can be difficult so I prefer specialized equipment. Also if one part fails, then you have to throw both out in most cases.
Once it's clear what you need then we can help you design the right system for you. What it costs will depend on what you need.