Waste Knots Want Knots
As a matter of principle, max out your health and armor, though you shouldn't need it all. Have plenty of ammo, too.
You will be working this mission with Packie and some of his boys against large groups of Bad Guys ("BGs"). You can't just hide and wait for them to do all the work because if Packie dies (or any of his crew as well, in the PC version), the mission is over, but you don't have to take any unnecessary chances, either.
The first group of BGs are outside, then Packie and his guys will wait for you to burst inside through closed doors. Just keep running to the opposite wall and you will be behind cover. Take out the BGs on the second floor first, then start working your way towards the stairs. As you go up the stairs, have your weapon up and ready to fire.
After you get into the office and pick up the money, more BGs will come pouring in downstairs, just run down the stairs and run fast towards the back and out the door on the left. Jump in the water and swim out to the boat you should see waiting out a little ways.
After you get in the boat, wait for Packie and then it's an easy ride to the finish with nobody chasing you.
A lot of thugs and police throwing a lot of lead in this one, but Niko doesn't ever seem to be in any real danger. Still, you will want to have full armor going in.
Niko can just crouch on the church steps and take out bad guys. Then you'll have to drive the hearse over to the graveyard without losing the casket out the back.
Despite all the cops and bad guys, you can go pretty slow and just follow the GPS and get there pretty easily.