Mmm Black...
I did the same and fell in love with my black limited and now I'm forever washing it!
Onto the gas - I'm about to get mine converted (I keep saying that) and I've been quoted everything from $3500 to $4200 so it varies. Plus if you are wanting to get Gas Injected then your looking more at the $5800 mark.
I'm in Vic and for me the Goverment Rebate is still going so I'll be getting back $2000. Of course this is only if the car is for private use (so not a company) and if the person who converts the car is certified.
Hope that helps.
Oh and I've rung a bunch of conversion places down here and they've had mixed emotions about doing Jeeps so you best find a good one that is happy and has done them before. Or, like me, go to a mechanic that is scared of my dad.