How to get the Ace mod self-interaction key to work

It's strange that your sergeant is copping fire from the fake insurgents as he should be out of a firing solution. Try parking the humvee to protect him from that direction.

As for the course, it is a tricky one and requires patience. Remember Arma2 is a military simulation, not a first person shooter so charging in when it's 5 against 1 will get you killed every time.

Move towards the town and slightly to the left so you get a good over-watch position down the main street. Stay prone or crouched and scan for two or three minutes. There should be a patrol on the far side of town but it's random so stay patient and keep watching. You want to take at least two of them out before they know where you are. Now you want to flank far left, keeping at least 100m from the town. You should be able to kill another two while they are focused on the direction you where before which leaves you one more to take out in urban combat. Move in slowly from the known to the unknown and watch your corners.

There are two very important things about this game you need to know if you are to be successful. Firstly, try to see them before they see you. Second, suppression is critical. If you are taking fire just open up like crazy in the general direction of the enemy, it keeps their heads down, reduces their accuracy and may even kill them.

I just got this working myself, although it took some help from the internet to get it working.

• Install Arma 2 and Arma 2: Operation Arrowhead.
• Close Steam completely, and then rerun it as an administrator (this is required to launch Arma 2 for the first time. You'll get a bad serial key error otherwise)
• Create folder called @DayZ in C:\Program Files (x86)\Steam\steamapps\common\arma 2 operation arrowhead
• Create a folder inside of that folder called Addons, and then download all the DayZ mod files from the DayZ website into that folder (So they should be located in C:\Program Files (x86)\Steam\steamapps\common\arma 2 operation arrowhead\@DayZ\Addons)
• Extract the files into the Addons folder. Make sure they are in the top level of the Addons folder or Arma 2 won't be able to find the files.
• Launch Arma 2 (you need to run Arma 2 first in order for Arma 2: Combined Operations to work, which is required for DayZ.
• Launch Arma 2: Operation Arrowhead from the Steam library, and run it as Arma 2: Combined Operation

That's all you'll need to do to get DayZ working. Chances are you'll want to filter out the non-DayZ games, which you can do by opening the Filter menu and setting mission to DayZ.

Sources: this video, this thread, and this thread.