Before you go to all the work, you may want to replace the trans mount, install a shift kit and convert the trans fluid from DEX III to DEX VI.
I had the same problem you are describing, getting worse in 2008, 88k miles. I did the above, and am now at 190k miles and have not had to repair or replace the trans. Cost was under $150 (shift kit, DEX VI, trans mount, trans filter) , under 3 hours labor, and it is fairly easy to do. I learned to do it right here at this forum from Dan Thurs.
2001 Bonneville SSEi, 219,000 miles.
Whats in my driveway:
1998 Chevy S10 4x4 ZR2, 1999 Olds Bravada, 2001 Pontiac Bonneville SSEi, 2007 Ford F-350 regular cab 2WD, 2008 BMW 335i coupe (Wife'* replacement for her Bonneville). The Bonneville is my favorite of all the cars in the driveway.