Normally, I'd back the die body off a half turn(no crimp), seat the new bullet style to the chosen depth in the case by adjusting the seater plug,back the seater plug off a turn,then adjust the die body for the amount of crimp wanted, leave the shell up in the die then screw down the seating stem snugly onto the bullet. This will but you very near or exactly at the proper adjustment. Adjust the stem slightly if you need to seat deeper after that.
If you were to just try to seat a new bullet length without backing off the crimp setting, chances are you would crimp and crush the bullet at the wrong depth and ruin a number of rounds in a trial and error process.
When all is said and done I prefer to seat and crimp in a seperate operation.