Why do you say "I would NEVER buy used parts"? Your statement is not logical. I mean if you can get a part that costs 1500 new for 100$. Well ACTUALLY you said it would be 1500 for the new part INCLUDING LABOUR for 1500.
Maybe you are dealing with an over-priced mechanic. Get a second opinion from somebody else. Its not like your car is broken down and in need of a tow truck. But I think you have a "wasteful" sort of attitude and a lack of patience. No offense but that is my experience of you.
I think your best bet is to get second and maybe a 3rd opinion from different mechanics. Dont be foolish and "give the car away" to some other dude that will get it fixed for 300 bucks.
And forget about tax deductions. That is fool's gold