Something like,
Also, you need to swap vertex color/normal/tex coord data. I'd still prefer it to rebuilding the mesh from scratch though, probably alot faster.
tx#=vertexX(vertex1)
ty#=vertexY(vertex1)
tz#=vertexZ(vertex1)
PositionVertex Vert2,VerteX(vert3),vertexy(vert3),vertezZ(vert3)
PositionVertex Vert3,tx,ty,tz
Also, you need to swap vertex color/normal/tex coord data. I'd still prefer it to rebuilding the mesh from scratch though, probably alot faster.