Tim:
I seem to be the only one talking here, but here goes:
You can't really power your stove or water heater with an inverter- too much power required which will run your batteries down quickly. And you shouldn't power your fridge either with 120V AC unless it is AC only (and that probably means it draws more power than a marine 12v Danfoss compressor unit). Also cabin lights are almost always DC.
So the first question is do you need AC power to run your fridge and how much? Small, Energy Star ones use maybe 175 watts when they run, but they only run part of the time. Larger, less efficient ones can draw more. Your laptop power supply probably draws 50-100 watts. So let's assume that your total instantaneous AC power needs are 250 watts. There are two ways to size and hook up an inverter.
Probably cheapest of the integrated inverter/chargers is a relatively small 1000 watt inverter/charger with a 55 amp charger like this one-
https://www.defender.com/product.jsp?path=-1|328|2289962|2289971&id=3115706. It won't charge your batteries as quick on generator power as a bigger and more expensive inverter/charger, so if you plan to do that often, install a bigger one with 100+ amps of charging capability.
Because it involves 120V AC I would recommend hiring a marine electrician to install it. But basically you hook up your house batteries to the inverter which lets it charge when AC is available or draw power from the batteries in inverter mode to produce AC. Then wire your incoming shore power to the inverter's AC input and the AC output to your 120V AC panel. There are much better ways to do this which isolate the big load appliances like the stove and hot water heater, but discuss these with your electrician.
Then when plugged into shorepower or your genset, the AC passes through the inverter to the AC panel. But when AC is not available the internal transfer switch lets the inverter generate it from DC and passes it to the AC panel.
This will cost $1,000+ installed for the one I indicated and more for a bigger one.
Another way is to get a couple of cheap, low power inverters. Use a 150 watt one plugged into a cigarette lighter socket for your laptop and a larger 200+ watt one for your fridge. This can be done for $100 or so and even cheaper if you only have a laptop to power with AC.
I cruised full time for a couple of years and even though I had a 2,500/100 inverter/charger I rarely used it- only for warming something up in the microwave. I did have a 150 watt lighter plug in model for my laptop.
David