Coolant in transmission, W124

[Art]

My '87 300E has fallen on hard times! The 2-3 upshift has been rough after warm up (but smooth when cold). Brought it to the local trans expert, who promptly found coolant in the trans! I installed a new Behr radiator approx. 2 years ago, and thought i would never worry about that again- didn't think the *&#@! trans cooler would ever be a problem. My game plan is to replace the radiator with one that is pressure tested, and pump out the trans fluid, while pumping in fresh. I'm concerned that the coolant may have damaged the friction plates, or their bond integrity- also that my rough shift may be do to corrosion in valve bodies. Any thoughts as to what I might expect? Car has 150K, and trans works fine other than the 2-3 shift. Thanks!

Art