Help with an auxiliary battery

[mtbing]

I'm wanting to install an auxiliary battery on my 1992 Eurovan CV. I think it is wired for one but i'm new to this so i'd thought i'd upload a couple images to get some advice.

The images are my main battery and the rear compartment (drivers side under the storage area) that I believe is where the aux battery goes.

My questions include:

1. Am I correct that i'm wired for an aux battery or is this simply a relay to power my existing equipment?

2. Is the black Bosch box a relay that will disconnect the battery when the ignition is off and reconnect for charging when the ignition is on?

3. How would the wiring run to an auxiliary battery?

4. Any recommendations on what battery to use, how to secure it, etc. would be appreciated.

5. Any idea what the white connector is for. I was thinking for things I don't have like furnace (fan) or hot water heater?

Thanks in advance for any help.