Turnaround time will be about 3-4 weeks in total.
You will need to provide us with the gerber files for the PCB you designed. You will also need to specify the thickness of the stainless steel. This will affect the solder paste amount. The aspect ratio for rectangular apertures should be 1.5 and an area ratio of 0.66.
Refer to these formulas as a basic rule of thumb:
Aspect Ratio = Width of Aperture (W) / Thickness of Stencil (T) [Should equal 1.5]
Area Ratio = Area of Pad (LxW) / Area of Aperture Walls (2 x (LxW) x T) [Should equal .66]