Its always the little things we overlook that kill us haha. Also I've thought a little bit harder about your predicament, and I've got a little bit more advice. These two weeks are not going to give you much improvement at all if any. Swimming is the hardest sport to train for because it requires tremendous amounts of yardage and time and long times out of the pool are detrimental to your whole stroke. That being said you probably aren't going to have the best swim of your life, however, the two weeks should not be wasted. I am mainly a sprinter when it comes to swimming anything above 500 yards I tend to stay away from, though I did train extensively for Sectionals(invitational meet) in both the 1000M and the Mile swims. Any amount you are going to race in the general rule of thumb for a swimmer in training is to do between 5-10 times that amount of distance every practice(broken up of course though I do not recommend this as you say you are not a strong swimmer). If I was in your situation I would practice every single day at least for the first week(you want as much as you are comfortable with). Equipment you should be using should be Pull paddles and Buoys to work on just your arms and a kick board to focus on your legs. A very generic practice would be a 300-600yard swim to warm up, this should be an easy comfortable swim working mainly on breathing and a correct long stroke that is smooth. After that take about 2-3 min at the most rest and do a 200yrd Pull(buoy between your legs and paddles on) continuing to force those long strokes. After that rest no more than 1 min. and do a 300-400yrd kick with the kickboard. Then do 3-7 100yrd swims on fast pace for you(I'm guessing 1:45-2:15 pace for your 100's) and resting 25 sec. in between each one. Then do a 300yrd warm down swim, this should be easy and you should really stretch out your entire body(reaching beyond what you think is the farthest you can reach LOTS OF ROTATION). After that stretch and make sure you are comfortable. This sort of workout can be modified to tailor your specific needs like i said it is very generic you can add to it or subtract from it this is just a very simplistic version of the practices I coach for my team. If you are swimming at a good pace with a smooth stroke you should be very tired after this, but you should not be overly sore if you start to hurt terribly in one spot(say your shoulder) then you might be swimming incorrectly(i.e. not enough rotation or dropping your elbows in the recovery part of your stroke). I really hope this helps out and feel free to message me if you seem to have extreme difficulties. Swimming is only as hard as you make it out to be, go in with a good mindset and a bottle of water and these practices and swims should be easy! Once again good luck!

p.s.If this is for a tri(I'm assuming it is) you should work hard on your pull sets with the paddles, because it is better to use mostly your arms in a tri swim since the rest of the race is almost entirely leg strength.