Get yourself a $30 Harbor Freight 1" x 30" belt sander, a selection of belts and a handfull of old or cheap knives to practice on. For the same amount of money as paying someone, you can learn to do it yourself!
I've had my belt sander a year or two and I don't hesitate to put any new blade on it for convexing (and that includes my old Swamp Rat Camp Tramp and several new Busses).
Stay sharp,
desmobob