AOD Dilemma

I have posted recently about possibly a PA valve body for my 112k AOD. Was playing cards with a Mercedes technician who said that if I drop the pan and put in new fluid during the valve body swap the AOD will more than likely slip and need a rebuild immediately because the old dirty fluid is likely the only thing holding the trans together at this point. Anybody have any experience with this?
If I put on the new valve body and the tranny starts slipping I think I'll shoot it!

Also, while I am asking dumb basic questions...how hard/how many hours to swap out stock headers for BBK shorty's without a lift?

Thanks!