Sell your TL and use the proceeds to buy one with a manual, it will cost you less money, take less time, and everything will work.

 

Regardless of which Generation this type of swap is attempted, it's not an easy DIY. Search related threads here, to see exactly what is involved. If money is no object, than no problem, you will probably find a shop willing to do it for you, but it would probably be VERY expensive. A less costly alternative might be to search for a 6 speed, buy it, and sell your car.

 

^ This, and nothing else.