Header Relocation

Hi all, Turning a wall that had a large picture niche/alcove into a wine cellar. I've established the wall is load bearing enough to the point that I will keep the header and jack studs for it but move it up to the top plate. My question is the best way to do this. The top plate is fairly well supported at each end and the span isn't that great but I'm nervous about just pulling out the header, cripples, etc. Do I just wedge some 2x4 at an angle in the center then jack everything up? Ceiling is easily 14ft.