I don't have this situation, but it's always been a curiosity to me.
I've been told several times never to change the fluid and filter in a transmission with burnt fluid. That it would just cause the tranny to slip and eventually die.
Now, I have actually had this happen to me once. The tranny was already slipping badly in my Monte Carlo. I changed the fluid and filter. I don't think I got even 20 miles before the transmission was slipping so badly I had to park the vehicle.
Is it a bad idea to change the fluid if it's burnt?

 

Mine was slipping slightly and shuddering pretty good. Fluid was burnt as well. I changed the fluid and all is good now for about a month now. If the tranny goes that soon after a change it was probably going to go soon anyhow.

 

Changing the fluid and filter is always a good idea. The benefits of new fluid will far outweigh any posiable issues that draining/refilling it may have. Say like loosing up trapped sludge.

The new fluid should look "new" even after being in service for a few hundred miles, if its dirty again, change it again. If it's burnt again, find out why.

The lubrication and pressure holding ability of new trans fluid over the old wore out fluid will do wonders for it. Especially if the fluid is burnt, burnt fluid is as bad as it gets.