While I don't know the details of your existing converter install, this thread may be of some interest:
http://www.fiberglassrv.com/forums/f...ter-48962.html
As far as an inverter, you need to figure out what you intend to run. I want a 1000W
microwave, so I am shopping for a 1500W inverter. The 12VDC current that feeds the inverter may be as large as 125 to 150 amps. The 12VDC wire between the inverter and the
battery, should be both large, and short. Then just plug into the inverter an extension cord to the load that you want to run. On a set of really good batteries, I would not run a 1000W load more then 45 minutes.