I was never able to avoid the alarms. Take over the TRMB and rescue Skywalker. Make sure to capture the turrets close to the TRMB before you start shooting. Take out the AT-ST with your 2 captured turrets and anything else that might get in your way. Be sure to use Luke's sight ability to scan ahead so you don't run into Patrols. Sneak around the patrols and take over every turret you come to. It will take a while, but I finished with 5000cp and many units. There are other post that tell you what the best way to take over turrets. I only lost 3 troopers.
Sacrifices are necessary for the ultimate goal.