cmt,

There are many YouTube videos illustrating various portion of what you need to do. I don't believe in doing shortcuts because it means coming back and revisit the problem sooner than never. Here is a list to do and materials.
1. Dig a big hole, enough to be able to bend the pipe line in the hole.
2. Cut out the broken part with a hacksaw blade or a pvc pipe cutter.
3. Buy a new slip/slip/threaded tee. Threaded side is for the riser threaded nipple. Glue tee to one side of the existing line after sanding and applying primer.
4. Buy short piece of pvc pipe, buy a compression coupling fitting for your size of PVC pipe.
5. Glue the piece of pipe into other side of tee. Watch the videos gluing pvc pipe and pay attention to the little things (primer and beveling pipe ends).
6. Cut the pvc pipe piece to about an 1" to 1 1/2" from the existing end of the pipe. Bend the pipe just enough to get the compression coupling on the pvc pipe and then slide the coupling into place on both pipes and tighten down.
7. Place a new riser on tee and remove the heads of that zone beyond the riser and flush out the zone.
8. Replace all the heads before burying the compression coupling. Run the system and check for leaking compression coupling leaking. If all is good cover and sod. GL Aloha