Some pool builders plumb the main drain to the skimmer rather than back to to the pump equipment and through a 3-way valve. The amount of suction between the skimmer and the main drain is then controlled by a rotating plate inside the skimmer (or in some cases an orfice) to cover/uncover one of the ports at the bottom of the skimmer.
Regarding the replacement of tile - it really depends on your skills. If you can re-tile a bathroom shower you should have no problem repalcing tiles around your pool.
If your new to pool ownership there is a descent CD (or down-loadable pdf file) available called Pool School. You can get it at www.poolrepair.com
I have no afiliation or intrests in promoting this site or CD. I only mention it because it helped me.
Mike
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