I guess it wasn't really that tough, I just had a bad strategy. In the level Nacho's Tanker, you land on a huge tanker and have to defuse some bombs and shoot it out with a shitload of thugs. I kept taking this one route through the ship, and I kept getting killed. But today, I took the other way, and the one bomb was right there, and as soon as I defused it, most of the enemies in that area disappeared. Today, luck was on my side, and I was finally able to wipe out the captain of the ship and after I eliminated the foreman and a few other thugs at the docks, I was all set. I'm finally back in Miami, and can buy more land and sell more drugs.
If I haven't said it before, if you like GTA-type games, buy Scarface for Playstation 2 or XBox. Definitely worth every penny. It's also out for the Wii, but I don't know how its controls work with it.