looking for some c5 z06 tr6060 options

Hi Jeremy,
I own a stock 2006 z06 and have been hearing a grinding and clunking noise coming from the rear of the car.An experienced mechanic told me it was the rear end(ring and pinion) that had some play in it.
The estimate to fix it was $2K since it takes 9-10 hours labor and $800-$1000 for parts.
The lube had been changed before but didn't fix the problem either.
Now i am thinking since i have to change the rear anyway,I would purchase your 3.90 gear rear end.I saw on your website the diff for z06 for $2995 or $3495 with the Quaife atp.
My questions are:
1.How many hours of labor is it to swap out my current rear end with a new one?
2.Is the 3.90 gear ratio recommended for street driving also?
3.Is the price before the core charge?
4.How much is the core charge?
5.How much would the cost be to just to buy a stock rebuilt rear end?

Thanks,

Chris

Hey can you shoot me a price for a 3.90 gear set for a c6 6 manual, and do you off the harden shafts