Basically you would remove the brick, dig down to where you can cut the incoming/outgoing lines, and with couplers re set the new valve. If your setup has timers, you would disconnect/reconnect the wiring. My advise would be to hire this done by a reputable lawn maintenance, landscaper, or handyman that is familiar with your set up. It will save you money in the long run as they have the materials needed along with the experience to make the fix. Less frustration for you as well. Simply priming and gluing pvc is pretty straight forward, but this project is a tad more involved than that. Ask around for someone reputable that has done their sprinkler/valve work.