Regardless of what you decide to do about doing a partial drain and refill or not, you must definitely switch to a non-stabilized form or chlorine such as bleach. No more trichlor tabs or dichlor shock powder. CYA take a long time to drop, so you are not going to see an appreciable change in it this year or maybe not even for several years. Having said that, in some pools, the CYA degrades over the winter into ammonia (which is another whole problem) but not in all pools and there is no way to predict in which pools this happens.

So, whether you partially drain or not, switch to bleach. But, you do need to order that good kit. Actually, even if you do a partial drain and refill, your CYA is still going to be around 75 or so and you will still need to be able to measure chlorine levels over 5, so go ahead and order it.

Let us know if you have more questions. We are glad to help!