<<Any suggestions on how/where to hook up the inverter to the second battery?>
>

When I removed my cigarette lighter to install my AC (don't ask), I went to
Walmart/FLAPS and bought a 5-foot cigarette lighter 'extension cord'.  I cut
off the plug end and spliced it into the old wiring.  The coiled cord now
sits in my glovebox, and when I need to recharge my phone I pull the cord out
and set the phone on the floor.  You could do the same thing -- attach a pair
of wires to the battery terminals, run the wires anywhere you want and splice
a cord onto the end of them.

BIll Marshall
85 GL Tiico
Bradenton FL