9 disc is pretty easy from everything I've read or those I've talked to. 11 and 12 disc is a lot tougher with machining involved.
I believe any trans shop can do the 9 swap.
How much horsepower and weight are behind the trans? I puked 2 of the 9 disc before I had Huber do mine right. 12,000 lbs, 630hp twins in the 39 Scorpion.