Hanna,

Good catch on the sand. The same water that kills the junk in your pool circulates over and over in your filter as well...killing anything in there. It's probably not a bad idea to open the lid of the filter and see if you have enough in there (usually about 2/3 to 3/4 full) and to check the general condition but, unless you see something obviously wrong, that sand will last another 10 years or more.

"Super Shock" is a brand name probably for Cal Hypo. It and Bleach are simply different forms of chlorine. The Cal Hypo adds calcium to your pool which you do not need in a vinyl pool.