mesh change of a skaarj????? help please

If I understood you correctly, you want to do a single player map with human opponents instead of Skaarj, right?
In that case, you'll have to write a new Scripted Pawn class. You could copy the code of the Skaarj and change the animations and so on to those of the human mesh you're using.

the trick is.....
open the mesh browser
select the mesh you want to use.
drop a skaarj in your map, select it.
open properties/display/mesh
click use, voila, your mesh selected is now used.
It will use alarm points
check this out

http://www.qtm.net/~dinwitty/DM-BossDance.ZIP

good example how its used, for UT only

Won't that cause problems because of differently named animations?

There are many animation names common between
models, and animations unique to each of the models. The choice to make is the mode (mesh) which is closet to the human model.
Yea, ingame stuff, I have tested it, does some strange things.
Patrol points are a different story, you can control what happens exactly.
As sugessted previous you may need to make another *.u class that supports the specific model.
You can study the code and change animation names to meet the need.
You dont need to recode the script, just look for animation names and change it.
If your going to do battle with this this model, potentially
animations might not fit, I am just trying to help reduce your workload.
Its a creative decision to determine what you need to do.
Selecting a mesh and studying animations names
to find the best match is okay.
Its a matter of what your idea needs to do and how much work you gotta do or not.
I just mention a little trick you can try, experiment with.