Before you start adjusting your chemistry, figure out if you want a CYA level at 100+. Read up on ben's best guess chart and other posts about CYA levels. the problem with high CYA levels is that it takes higher chlorine levels to both sanitize and shock. while CYA is somewhat of a personal choice, I think you'll be hard pressed to find people with pools on this forum maintaining above 90ppm. You'll probably find a few, but I think you'll find most in the 40-60 range. Others feel free to chime in if you think that estimate is off. SWG can influence the desired level of CYA as well.

If you are going to want to lower your CYA level, only way to do it is a partial drain and refill. Since you will be introducing new water if you do that, might make more sense to do the drain first and then react to the new water chemistry. Might help your ph and alk. Would be a shame to work to get them leveled only to decide to drain and refill, and then have to deal with the new chemistry.

If you want to drain, you can figure out how much by 1) figuring out the size of the pool and 2) using the bleachcalc program found on mswsmith's postings (or use google search on 'bleachcalc') to calculate (go to other calcs).