As a crop scientist & experienced landscaper, i think i understand your need.
Depending on the type of mulch you may require for your garden bed, (i.e live mulch or composting).
Garden digging will be very minimal to concentrate on the top soil considering soil type/nature.
Your project completion will be based on the bed and garden area at an average completion duration of 48 hours per Hectare for both digging and spreading.
I will be glad if you will contact me for further details on your project. Thank you.