how do I replace this broken slide valve

[GoGoddess]

I have fixed sprinklers before but this is my first slide valve replacement Maybe I want it too easy because I dont want to saw off past where the old slide valve was. (The first pic shows how the under support is right at the spot where the plumbing for the slide valve comes out.) And yet part of the old slide valve is stuck on there in just the wrong place

Any and all ideas are greatly appreciated, even if it means more work than I initially thought of

Patrick and Heather