1996 Trans help please!!!!

I took my 1996 Tahoe (168,000 miles) to the Trans shop today to get the oil a filter changed. The car has had a vibration in it when I am between 68 to 73 MPH. Below 65 and above 75 the sound and vibration is gone. It sounds like a small deep rumble with a slight vibration that is NOT coming from the steering wheel. The sound and vibration is the same going up hill, down hill, foot on the gas or off. When the Trans shop pulled the pan there was fine mettle shaving and some dark material in the pan. They tore the filter a part and showed me the mettle shaving trapped in the filter. They said the tork converter was going bad and I should have the Trans rebuilt. The cost $1,600 to $2,500. Is it a possible the Trans is real bad and making the noise and rumble at the speed of 68 to 73 only? How easy it to swap the Trans and tork converter out at home? I have most normal tools and have swapped 2 speed 1964 Chevy type out before. Thanks Dave

It sounds like a planetary gear going bad, That sounds a bit high in price I had my rebuilt with heavy duty parts for about $1500. The trans code should be 4L60E and is a very common electronically controlled trans. Look around for a better deal from a shop with a good reputation.