A6 4.2 Trans Malfunction
 

I have a 2001 A6 4.2L with 93k, just bought it. No trans issues were evident on the test drive @ 91k but now in 1st gear the trans started freewheeling then caught with hard engagement, then yesterday got so bad the car would barely move forward from a stop. I haven't hammered on the vehicle, just normal driving. I took to my favorite repair shop and the diagnosis was a bad A-drum, and the solution to rebuild with an updated version of the drum and TC rebuilt/seal kit for good measure. Estimate = $3500 total. Reasonable diagnosis/cost?