New sink is where the old sink was. I've taken out the visible galvanized iron and replaced it with PVC. Where the sink waste goes in to the wall, it connected in a tee. Now there is a wye/45* combo.
My dilemma is this: even if I manage to get the 2-1/8" holes drilled through the 4 studs to the left of the waste line, I'll never be able to thread the vent line through the holes I drill as PVC is not flexible and there isn't enough room to lay pipe 7" down and 5 feet across when you only have 16" clearence between studs.
I can post pictures to a web page if you need to see what I'm talking about.