Welcome
From your description that turbo is totally farked!
You have a few options from here.
1.Wreckers for a second hand turbo. If you do this make sure it's from a B series as the FG onwards ran a smaller exhaust wheel and it won't run quite right without a retune.
2. New. You've priced them. That's fairly ballpark. If you're not planning on modding it stick with the GT3582 and love life.
3. Go bigger and better. GTX3582 or go the gtx3576 for better response but you'll need to tune with both of these. Plus the supporting mods etc etc.
As for fitting it isn't hard. It's time consuming but if you're good with the spanners you'll be ok.
Most importantly. Take the filter out of your oil feed line or better yet go aftermarket line and keep it away from the exhaust manifold.
Also forgot to mention that you'll want a completely new gaskets for the manifold and turbo to manifold plus all new studs and washers. Don't reuse the stock sh*t unless you like tightening things or exhaust leaks.