If you have the Sten (which looks like a silenced Uzi), then you're good to go. Start out by fragging the guys near the first building you come to. You need to keep your distance, and double tap them as stealthily as possible. Once you do this, I think there is some health in the barn structure.
Once you've done this, follow JuiceRocket's suggestion and head towards the right of the barn. I always followed the very perimeter of the map along the rock wall. Keep rounding the rock wall until you see the guard tower near the tunnel. The next step is to take out the Nazi in the guard tower. You'll have to crouch your way to him. Once you get a clean shot, frag him.
The way I get into the tunnel without being spotted is to circle around the tower guard you just fragged and down the hill directly behind the tree at the bottom of the hill. Keep an eye out for the guards near the bridge and time their patrols so that you can make it to the tunnel without being spotted.
Once you make it to the tunnel their are two more guards to deal with. Don't shoot them yet. ;) Just time it so that you can get to the door on the right (in the tunnel) without them seeing you.
Proceed thru the door, go down the tunnel and up the ladder. Once you top the ladder, get in crouch mode and make your way just past the little hillcrest on your left. You will start a decline. Stop there because a guard will come in plain sight before long. He will be patrolling the area, and I always like to pop him when heâ€™s just outside the rock wall right below you. Once youâ€™ve dispatched him, take out the guard near the M42 gun emplacement.
From there, youâ€™ll need to crouch-walk all the way back to the right where youâ€™ll find a silenced sniper rifle- the Snooper I believe.
Now, take out the guard in the tower (with the Snooper, and remember, one shot, one kill) above the guy you last took out near the M42. Next, sneak your way near the tower and use the Snooper to take out the guys you left alone near the tunnel. One shot each and be quick about it.
To the right of the guard tower youâ€™ll see a elevated building and fence. In that building is a guard that can sound the alarm as well, so use the Snooper take him out as quickly as possible. It usually will take two shots to bring him down.
NOTE: you may be able to take this guy out before the guys near the tunnel.
Once inside the compound, there will be one guy on the water tower, and if youâ€™re lucky, youâ€™ll have one or two more shots left in the flooper to take him out. There will be one more guy in the building directly across from the entrance to the compound.
Once you take out the guy in the building, thereâ€™s one more guard patrolling the platform where the truck is parked. Take him out silently, and then hop in the back of the truck.
Thatâ€™s it, on to the next level.
BTW, RTCW is one of my favorites!