Hi karmi,
The inverter should be sized at 125% of the greatest load it will have to carry. I.E. a 1200 watt hair drier needs a 1600 watt inverter. Pure Sine wave is preferable but not 100% essential. Since Xantrex makes a 2000 watt psw for $355. it is a no brainer to go that direction, unless 300 watts or less is needed.
Installation can be as simply as plugging into a cigarette lighter (no more than 150 watts available--even if the inverter can do more). Or you can have a large inverter tied in directly to the battery bank--with a system of plugs or an additional transfer switch.
Decide how much wattage you need--and then ask for specifics on installation and brands.