If there's a serious problem in the gearbox, it will likely be more cost effective for you to simply buy a Bergey Excel or Proven 6600 or ARE 442, or build your own 17 or 20 foot machine. With a VERY sturdy tower to match. Or, get a new

As for providing your own "grid" with an Outback inverter -- Enertech machines were grid synchronous. Even their new E6 5kw machine is grid synch, no inverter (pretty cool!). But are you sure that your Outback is capable of performing 'stiff' enough for a grid synch turbine of that size? Have you contacted Outback to ask? Outback will be the 'horse's mouth' on your question, and either Enertech itself or Lake Michigan Wind and Sun will be able to tell you exactly what you have -- and what you don't.