Utilizing accessory battery

Howdy all,
I have a 1995 E350 Ford former paratransport van. The wheelchair lift has been removed but the accessory battery is still installed.
How can I go about getting the following done:

  • install a switch to isolate this battery from the engine (so the starting battery doesn’t get drained)
  • install a meter on the accessory battery to determine charge level
  • install usb & 110 volt outlets from the accessory battery
    I am very handy but this is out of my depth. Is this something a regular auto mechanic can do?

All very simple You need to go on Amazon Buy a battery isolation switch. You can buy a meter on there as well You then need to buy a 12 volt inverter. Only buy a “”pure signwave inverter. 1000 watt is small but enough for certain small appliances. A 2500 watt inverter is needed to use a microwave or an AC unit. Also you need atleast 100 ampp hour battery. Thousands of video how to do it all on toutube or patrion. Wire id important, very impartant to use copper . I wuldnt go smaller than 4 guage for alternator to battery charger