hahaha....to be honest i think i completed that mission the coolest way you can do it!
first i tried running over all the guards...but i died
i tried drive bys and killin all the guards but the army vehicles always ran over me...
so this is what i did, i got a bike PEG 600,
stoped a couple of yards away and sniped the dude inside the tank. took off and killed all the guards with one drive by, well not all of them i just swilred arond and capped all of them. then made the army vehicles chase me as far as a i could, jumped out the bike and got into the inferno i had parked there(all part of the plan) drove as fast as i could back to the tank, got on and the rest was easy, i shot everything that moved, and got like 5 stars rating FBI chasing me and everything, but after i parked it in the garage everything was cool again..