"Show me a Rose, or leave me alone.." - Bert Kalmar & Harry Ruby, 1922
Rose, welcome to the forums. Read up on the archives if you're so inclined, you'll learn a great amount.
First, TWO GALLONS A WEEK? You sure you're not missing the radiator and pouring it on the ground?
Your somewhat exorbitant quotes may well be due to your chromosome difference from the weaker sex (us guys). $7,000 should buy a new motor, new interior, new tires, new transmission, a MAACO Ambassador paint job with your choice of color on the chrome, and probably an air freshener thrown in to boot.
If you are loosing that much coolant every week, it's gotta be going somewhere. Take your car to a qualified (Read: Different) mechanic and ask them to check all the radiator hoses and connections. It may be leaking out of one of the hoses when under pressure and hot, and blowing away in the slipstream while the car is moving.
Ask them to check the area around the water pump. A gasket there that leaks could also be the culprit.
I'd think that if your car had a SERIOUS problem, that it would be exacerbated over time and get worse and worse - is there any white smoke blowing out the tailpipe? Does the car's coolant temp show an alarming tendancy to climb to stratospheric heights?
PLEASE get a qualified 2nd or 3rd opinion before you succumb to the blandishments of what appears to be a cousin of Jesse James before you replace the motor or sell the car.