Monday the 8th of October, or Monday the 1st? Either way you need to act really fast. Woodsters suggestions would be okay, especially if you dont have time to stay on task and follow through with the following.
I would do it the way manufacturers suggest. Drain the oil and pull the injectors. While the oils draining.... If there is water in the fuel tank, disconnect the fuel feed line to the main filter. Drain the fuel filter, or replace it. Hook up a line to a auxiliary fuel supply to the main filter. Open the fuel bleeder. Remove the air cleaner and blow it off or knock the water off it. Put it back on. Put a wrench on the crank pulley and turn the engine slowly by hand at least 4 turns, feeling for heavy resistance. If its real hard to turn or feel its hitting something, the motor needs to come apart (right away). If it turns over okay, continue... Take the wrench off, and crank it with a starter for 15 seconds to clear the water out of the cylinders. Youll probably see it blast out the injector ports. Watch for fuel at the bleeder. Squirt some oil (squirt can, 5 squirts, or pour a few teaspoons full) of oil in the injector ports, let sit a few minutes. Any oil is okay, but MMO is really good. If you have plain old engine oil use that. Dont go running for hours looking for MMO or something, you need to save the engine. Now crank the engine 30 seconds to clear the oil. Watch the fuel bleeder.
This cranking is very critical. Any fluid left behind, oil or water either one, could cause hydraulic lock and break the engine. Cranking it over on the starter (with a decent battery) it will really blow a lot of air through and clear the cylinders. Refill the sump with oil. I would leave the oil filter alone, if it went under not running the oil circuit still has oil in it. If it was running when it went under, and it still turns over, replace the oil filter. There is going to be water inside anyway, the main objective right now, is to get it running as soon as possible. Time is of essence.
Its full of fresh oil, now crank it till you see fuel at the bleeder, tighten bleeder, reinstall injectors, try to start it. Once it starts, let it run on the aux tank while you check your fuel tank for water. If the tank doesnt appear water logged, try hooking it up and reconnect it to your engine. Now let it run until it gets good and warm, watching and listening for any problems. Shut it down and change the oil and filter. Check your fuel filter water trap. Keep checking it. Start it back up and run it around an hour while you keep checking the trap and watching the engine. Change the oil and filter again. The objective with bypassing the main fuel tank is simply to get the motor running asap. You can deal with a wet fuel tank later, first is to save the engine. If your not seeing any water at the tank, go ahead and run it, with the understanding a large gulp of water is going to shut it down and youll have to bleed the entire fuel system, not of air but water (very time consuming).
Water will rust the cylinders real fast, as well as other internal moving parts that are bare metal. Oil can only protect it so much in a submersion situation. Getting it running and getting it hot, as soon as possible, is the only way to clear out the major water and burn off the rest. The only other alternative is disassembling the engine. The oil changes are to rid the engine of water. You change it hot when the water is held in suspension, not after its cold. Filter too. The heat, the oil changes, the air turbulence inside, will all work to rid it of water and put good protective oil onto the surfaces.
Good luck.