This mission is easy and a lot of fun. Definitely my favorite of the Co-Op missions so far. It's night and it's raining. Your night vision really helps on this mission. I completed this one by myself in a local game today - spawned as a Grenadier with a suppressed M468.
Objective - Destroy Comm. Tower: You will be inserted behind enemy lines, so any suppressed weapons will really help. Move forward and clear out the back side of the hill, then head up the hill to plant your charge on the communications unit. Do this within a few minutes or the enemy will call in helicopter support.
Objective - Save Allied Tank: I'm not sure, but I believe this is the secondary objective. You need to move quickly, taking out only the enemies that are between you and the east ADAT. Suppressed weapons are recommended so other enemies don't hear you and flank. Have a grenadier take out the ADAT (careful, it WILL shoot at you, although I don't believe I was ever actually hit by it).
Objective - Destroy Artillery: Having already destroyed the east ADAT, you're halfway done with this objective already. Sneak through the trenches with your suppressed weapon, taking out only those enemies between you and the next ADAT. Again, have a grenadier take out the ADAT.
Objective - Eliminate Remaining Enemies: Most of these will be in or near the blown up building next to the last ADAT. Take them out and it's mission complete. Easy street.