LOL! That's a lot of money for something that can be done in 2 hours max.
Radiator: $50 Ebay or $100 OEM
Upper/Lower radiator hoses: ~$30 at NAPA
Lilse funnel for coolant bleeding: $25 Amazon
Thermostat: $25 OEM
Floor jack, 2 jack stands, basic 3/8 metric ratchet set: $170 Harbor Freight

And then you'd end up with a floor jack and the essential tools you need to do probably 85% of the stuff on these cars.
This is all just a matter of unbolting and removing the fan shroud, thermostat, removing the upper/lower rad hoses, removing the transmission fluid lines to the rad, replacing the radiator, and then reassembling in reverse.

 

I went to another shop and they said my car has to change both the radiator and the condenser because they cant just change the radiator for this car. Does this sound like they are trying to rip me off?
Also, they said there's water in my transmission so I need to flush and refill the transmission. Then after driving it for a month or two, I should give it another flush.
He cannot guarantee if this will fix the problem so he said it's up to me to go with the fix or not.
Radiator, condenser, and transmission flush for $750.

Not knowing how to fix a car sucks....haha

 

There's only so much you can get asking questions on an internet forum. At some point you have to decide either to figure out how to fix it yourself by reading the factory service manual's step by step illustrated guide on how to do the job (https://www.nicoclub.com/FSM/G35/Sedan/2008/), watching some YouTube videos/Googling stuff, and finally posting questions on here once you start if you can't figure something out.

...Or just pay somebody what they want to fix it.
...Or trade it to a dealership for a huge loss where they'll spend $200 fixing it and have it for sale for $2000 more the next day
...Or get rid of the car at a huge loss to some kid who will spend 2 hours and $200 fixing it and have an obtainable dream car

 

Yea,I understand. I dont mind paying a mechanic to fix it (I mean they gotta make money too, you know?), but just worried that problems are gonna keep coming outta this car.
Should really consider just trading it in, even if its for a loss, and get a new car. Always wanted a WRX so maybe I should just pull the trigger and get it....
Well, thanks for all your input man. It really helped.