Torque converter I *think* is on it's way out... need some options
 

Ok so for some reason this car decides that the TC (or so I think) will go just as I was about to put it for sale as I'm upgrading vehicles (e70) which I'll have in a couple of days. Just my luck I guess. It's the 2002 e53 x5 4.4L. I don't think I can sell the vehicle without disclosing this to the buyer so I think I'm leaning towards repairing it before sale.

Lately in the morning when the vehicle is cold(sometimes very rarely actually) I hear a whining/whirring sound coming from I imagine is the TC.
Mostly when warming up but I've also heard it during warmed up temp a slight whine shifting from gear 1-2. There's no slippage that I can note but the car does sometimes feel like it's going over a slight bumpy road.

A few months ago I had like a studdering issue when accelerating (very slight as well) so I changed the tranny fluid and that actually made the issue go away. It was working great until now.
The car only has 122k KM (approx 76k miles) which is quite low for it's age.

I'm wondering if anyone can suggest a good place to buy the replacement part or what are your thoughts on a used part?
Also approx how much time would I expect the labor to take?

I'm having the same issue, any luck with what was causing this to happen?